octeontx2-af: update cpt lf alloc mailbox

The CN10K CPT coprocessor contains a context processor
to accelerate updates to the IPsec security association
contexts. The context processor contains a context cache.
This patch updates CPT LF ALLOC mailbox to config ctx_ilen
requested by VFs. CPT_LF_ALLOC:ctx_ilen is the size of
initial context fetch.

Signed-off-by: Srujana Challa <schalla@marvell.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>