net: systemport: Add support for WAKE_FILTER

The SYSTEMPORT MAC allows up to 8 filters to be programmed to wake-up
from LAN. Verify that we have up to 8 filters and program them to the
appropriate RXCHK entries to be matched (along with their masks).

We need to update the entry and exit to Wake-on-LAN mode to keep the
RXCHK engine running to match during suspend, but this is otherwise
fairly similar to Magic Packet detection.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>