net: pch_gbe: Remove {read,write}_phy_reg HAL abstraction

For some reason the pch_gbe driver contains a struct pch_gbe_functions
with pointers used by a HAL abstraction layer, even though there is only
one implementation of each function.

This patch removes the read_phy_reg & write_phy_reg abstractions in
favor of calling pch_gbe_phy_read_reg_miic & pch_gbe_phy_write_reg_miic
directly.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Signed-off-by: David S. Miller <davem@davemloft.net>