octeontx2-af: fix a issue with cpt_lf_alloc mailbox

This patch fixes CPT_LF_ALLOC mailbox error due to
incompatible mailbox message format. Specifically, it
corrects the `blkaddr` field type from `int` to `u8`.

Fixes: de2854c8

 ("octeontx2-af: Mailbox changes for 98xx CPT block")
Signed-off-by: Srujana Challa <schalla@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>