net: pch_gbe: Remove PCH_GBE_MAC_IFOP_RGMII define

The pch_gbe driver currently presumes that the PHY is connected using
RGMII, and would need further work to support other buses. It includes a
define which is always set that conditionalises some of the
RGMII-specific code regardless. Remove it. If we do ever support
different MII buses then preprocessor defines won't be the best way to
select between them anyway.

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