octeontx2-af: Display NIX1 also in debugfs

If NIX1 block is also implemented then add a new
directory for NIX1 in debugfs root. Stats of
NIX1 block can be read/writen from/to the files
in directory "/sys/kernel/debug/octeontx2/nix1/".

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