net: phy: marvell: Fix init function for m88e1145

Commit a058052c changed the generic phy_reset() to clear all bits in
BMCR. This inevitably clears the ANEG bit. m88e1145 requires any
change to ANEG bit to be followed by a software reset. This seems to
be different from other PHYs. Implement read-modify-write procedure
for this PHY init.

Signed-off-by: York Sun <york.sun@nxp.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>