net: bcmgenet: remove handling of wol interrupts from isr0

The bcmgenet_wol_isr() handler performs the necessary processing for
waking from a GENET event.  There is no necessary functionality behind
servicing the UMAC_IRQ_MPD_R event in the handling of isr0.  Therefore
the code that unmasks and masks this interrupt and that gets invoked
in response to it is removed by this commit.

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