net/octeontx2: fix optimal default SQE buffer count

net/octeontx2: fix optimal default SQE buffer count

Patch extends minimum supported max_sqb_count devarg value
such that it can limit the max sqb count to 8 buffers and
also defines NIX_DEF_SQB and uses it to compute the number
of sqe buffers required for the egress traffic.

NIX_DEF_SQB is defined as 16 which is optimal across multiple
octeontx2 platforms to scale up the performance proportional
to the corresponding port/queue to lcore mappings.

Fixes: fb0198b7dc07 ("net/octeontx2: add devargs parsing functions")
Signed-off-by: Vamsi Attunuru <vattunuru@marvell.com>
Acked-by: Jerin Jacob <jerinj@marvell.com>