ucc_geth.c: Fix upsmr setting in RMII mode

If using the UCC on a MPC8360 in RMII mode, don;t set
UCC_GETH_UPSMR_RPM bit in the upsmr register.

Signed-off-by: Heiko Schocher <hs@denx.de>
Acked-by: Li Yang <leoli@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>