bgmac: Utilize BRCM_PSEUDO_PHY_ADDR

What BGMAC defines as BGMAC_PHY_NOREGS is in fact the Broadcom Ethernet
switches' pseudo-PHY address (30), utilize the newly introduced constant
from brcmphy.h

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