octeontx2-af: Fix mailbox errors in nix_rss_flowkey_cfg

In npc_update_vf_flow_entry function the loop cursor
'index' is being changed inside the loop causing
the loop to spin forever. This in turn hogs the kworker
thread forever and no other mbox message is processed
by AF driver after that. Fix this by using
another variable in the loop.

Fixes: 55307fcb ("octeontx2-af: Add mbox messages to install and delete MCAM rules")
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>