octeontx2-af: Setup MCE context for assigned NIX

Initialize MCE context for the assigned NIX0/1
block for a CGX mapped PF. Modified rvu_nix_aq_enq_inst
function to work with nix_hw so that MCE contexts
for both NIX blocks can be inited.

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