Revert "net: bcmgenet: remove unused function in bcmgenet.c"

This reverts commit e2072600.

This commit restores the previous implementation of Hardware Filter
Block functions to the file for use in subsequent commits.

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>