octeontx2-af: Add mbox API to validate all responses

Added a new mailbox API which goes through all responses
to check their IDs and response codes.

Also added logic to prevent queuing multiple works to
process the same mailbox message. This scenario happens
when AF is processing a PF's request and menawhile PF
sends ACK to AF sent UP message, then mbox_hdr->num_msgs
in the PF->AF DOWN mbox region will be nonzero and AF
will end up processing PF's request again. This is fixed
by taking a backup of num_msgs counter and clearing the
same in the mbox region before scheduling work.

Signed-off-by: Subbaraya Sundeep <sbhatta@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>