net/phy: Fix 88e1111 copper/fiber selection in RGMII mode

MII_M1111_HWCFG_FIBER_COPPER_RES is a bit of MII_M1111_PHY_EXT_SR, not
MII_M1111_PHY_EXT_CR.

Signed-off-by: Wang Jian <lark@linux.net.cn>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>