net/octeontx: add unicast MAC filter

At BGX, DMAC filter table can be enabled to allow defined hosts.
Patch implements 'mac_addr_add' and 'mac_addr_remove' ops to
add/remove MAC filters which uses BGX DMAC filter table.

Signed-off-by: Sunil Kumar Kori <skori@marvell.com>
Acked-by: Harman Kalra <hkalra@marvell.com>