net: bcmgenet: restore HFB filters on resume

The Hardware Filter Block RAM may not be preserved when the GENET
block is reset during a deep sleep, so it is not sufficient to
only backup and restore the enables.

This commit clears out the HFB block and reprograms the rxnfc
rules when the system resumes from a suspended state. To support
this the bcmgenet_hfb_create_rxnfc_filter() function is modified
to access the register space directly so that it can't fail due
to memory allocation issues.

Fixes: f50932cc ("net: bcmgenet: add WAKE_FILTER support")
Signed-off-by: Doug Berger <opendmb@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>