octeontx2-af: Display CGX, NIX and PF map in debugfs.

Unlike earlier silicon variants, OcteonTx2 98xx
silicon has 2 NIX blocks and each of the CGX is
mapped to either of the NIX blocks. Each NIX
block supports 100G. Mapping btw NIX blocks and
CGX is done by firmware based on CGX speed config
to have a maximum possible network bandwidth.
Since the mapping is not fixed, it's difficult
for a user to figure out. Hence added a debugfs
entry which displays mapping between CGX LMAC,
NIX block and RVU PF.
Sample result of this entry ::

~# cat /sys/kernel/debug/octeontx2/rvu_pf_cgx_map
PCI dev         RVU PF Func     NIX block       CGX     LMAC
0002:02:00.0    0x400           NIX0            CGX0    LMAC0

Signed-off-by: Rakesh Babu <rsaladi2@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: Subbaraya Sundeep <sbhatta@marvell.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>