octeontx2-af: Drop rules for NPC MCAM

NPC exact match table installs drop on hit rules in
NPC mcam for each channel. This rule has broadcast and multicast
bits cleared. Exact match bit cleared and channel bits
set. If exact match table hit bit is 0, corresponding NPC mcam
drop rule will be hit for the packet and will be dropped.

Signed-off-by: Ratheesh Kannoth <rkannoth@marvell.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>