perf: Fix usages of profile_cpu in builtin-top.c to use cpu_list

profile_cpu was left over from an earlier implementation that
supported running perf top on a single CPU.  profile_cpu was no
longer set by any switch and usages of it resulted in dead code.

Instead, convert the code to use cpu_list, which is set by the
-C <cpu_list> option.

Also improved the printing of nr_cpus and cpu_list by correcting
the plurals.

Signed-off-by: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: a.p.zijlstra@chello.nl
Cc: acme@redhat.com
LKML-Reference: <1289269245-9388-1-git-send-email-cjashfor@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>