powerpc/cacheinfo: Remove the redundant get_shared_cpu_map()

The helper function get_shared_cpu_map() was added in

'commit 500fe5f5 ("powerpc/cacheinfo: Report the correct
shared_cpu_map on big-cores")'

and subsequently expanded upon in

'commit 0be47634 ("powerpc/cacheinfo: Print correct cache-sibling
map/list for L2 cache")'

in order to help report the correct groups of threads sharing these caches
on big-core systems where groups of threads within a core can share
different sets of caches.

Now that powerpc/cacheinfo is aware of "ibm,thread-groups" property,
cache->shared_cpu_map contains the correct set of thread-siblings
sharing the cache. Hence we no longer need the functions
get_shared_cpu_map(). This patch removes this function. We also remove
the helper function index_dir_to_cpu() which was only called by
get_shared_cpu_map().

With these functions removed, we can still see the correct
cache-sibling map/list for L1 and L2 caches on systems with L1 and L2
caches distributed among groups of threads in a core.

With this patch, on a SMT8 POWER10 system where the L1 and L2 caches
are split between the two groups of threads in a core, for CPUs 8,9,
the L1-Data, L1-Instruction, L2, L3 cache CPU sibling list is as
follows:

$ grep . /sys/devices/system/cpu/cpu[89]/cache/index[0123]/shared_cpu_list
/sys/devices/system/cpu/cpu8/cache/index0/shared_cpu_list:8,10,12,14
/sys/devices/system/cpu/cpu8/cache/index1/shared_cpu_list:8,10,12,14
/sys/devices/system/cpu/cpu8/cache/index2/shared_cpu_list:8,10,12,14
/sys/devices/system/cpu/cpu8/cache/index3/shared_cpu_list:8-15
/sys/devices/system/cpu/cpu9/cache/index0/shared_cpu_list:9,11,13,15
/sys/devices/system/cpu/cpu9/cache/index1/shared_cpu_list:9,11,13,15
/sys/devices/system/cpu/cpu9/cache/index2/shared_cpu_list:9,11,13,15
/sys/devices/system/cpu/cpu9/cache/index3/shared_cpu_list:8-15

$ ppc64_cpu --smt=4
$ grep . /sys/devices/system/cpu/cpu[89]/cache/index[0123]/shared_cpu_list
/sys/devices/system/cpu/cpu8/cache/index0/shared_cpu_list:8,10
/sys/devices/system/cpu/cpu8/cache/index1/shared_cpu_list:8,10
/sys/devices/system/cpu/cpu8/cache/index2/shared_cpu_list:8,10
/sys/devices/system/cpu/cpu8/cache/index3/shared_cpu_list:8-11
/sys/devices/system/cpu/cpu9/cache/index0/shared_cpu_list:9,11
/sys/devices/system/cpu/cpu9/cache/index1/shared_cpu_list:9,11
/sys/devices/system/cpu/cpu9/cache/index2/shared_cpu_list:9,11
/sys/devices/system/cpu/cpu9/cache/index3/shared_cpu_list:8-11

$ ppc64_cpu --smt=2
$ grep . /sys/devices/system/cpu/cpu[89]/cache/index[0123]/shared_cpu_list
/sys/devices/system/cpu/cpu8/cache/index0/shared_cpu_list:8
/sys/devices/system/cpu/cpu8/cache/index1/shared_cpu_list:8
/sys/devices/system/cpu/cpu8/cache/index2/shared_cpu_list:8
/sys/devices/system/cpu/cpu8/cache/index3/shared_cpu_list:8-9
/sys/devices/system/cpu/cpu9/cache/index0/shared_cpu_list:9
/sys/devices/system/cpu/cpu9/cache/index1/shared_cpu_list:9
/sys/devices/system/cpu/cpu9/cache/index2/shared_cpu_list:9
/sys/devices/system/cpu/cpu9/cache/index3/shared_cpu_list:8-9

$ ppc64_cpu --smt=1
$ grep . /sys/devices/system/cpu/cpu[89]/cache/index[0123]/shared_cpu_list
/sys/devices/system/cpu/cpu8/cache/index0/shared_cpu_list:8
/sys/devices/system/cpu/cpu8/cache/index1/shared_cpu_list:8
/sys/devices/system/cpu/cpu8/cache/index2/shared_cpu_list:8
/sys/devices/system/cpu/cpu8/cache/index3/shared_cpu_list:8

Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210728175607.591679-3-parth@linux.ibm.com