net: bcmgenet: fix mask check in bcmgenet_validate_flow()

VALIDATE_MASK(eth_mask->h_source) is checked twice in a row in
bcmgenet_validate_flow(). Add VALIDATE_MASK(eth_mask->h_dest)
instead.

Fixes: 3e370952 ("net: bcmgenet: add support for ethtool rxnfc flows")
Signed-off-by: Denis Efremov <efremov@linux.com>
Acked-by: Doug Berger <opendmb@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>