octeontx2-af: Add array index check

In rvu_map_cgx_lmac_pf() the 'iter', which is used as an array index, can reach
value (up to 14) that exceed the size (MAX_LMAC_COUNT = 8) of the array.
Fix this bug by adding 'iter' value check.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 91c6945e

 ("octeontx2-af: cn10k: Add RPM MAC support")
Signed-off-by: Aleksandr Mishin <amishin@t-argos.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>