octeontx2-pf: Remove unnecessary bounds check

octeontx2-pf: Remove unnecessary bounds check

active_fec is a 2-bit unsigned field, and thus can only have the values
0-3. So checking that it is less than 4 is unnecessary.

Simplify the code by dropping this check.

As it no longer fits well where it is, move FEC_MAX_INDEX to towards the
top of the file. And add the prefix OXT2.  I believe this is more
idiomatic.

Flagged by Smatch as:
  ...//otx2_ethtool.c:1024 otx2_get_fecparam() warn: always true condition '(pfvf->linfo.fec < 4) => (0-3 < 4)'

No functional change intended.
Compile tested only.

Signed-off-by: Simon Horman <horms@kernel.org>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Reviewed-by: Hariprasad Kelam <hkelam@marvell.com>
Link: https://patch.msgid.link/20260119-oob-v1-1-a4147e75e770@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>