net/bnxt: add L2 filter alloc/init/free

net/bnxt: add L2 filter alloc/init/free

Add the L2 filter structure and the alloc/init/free functions for
dealing with them.

A filter is used to identify traffic that contains a matching set of
parameters like unicast or broadcast MAC address or a VLAN tag amongst
other things which then allows the ASIC to direct the  incoming traffic
to an appropriate VNIC or Rx ring.

New HWRM calls:
bnxt_hwrm_clear_filter:
	Free a L2 filter.

bnxt_hwrm_set_filter
	Allocate an An L2 filter or a L2 context.

Signed-off-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Signed-off-by: Stephen Hurd <stephen.hurd@broadcom.com>
Reviewed-by: David Christensen <david.christensen@broadcom.com>