ARM: gemini: remove unnecessary mdio-gpio includes

Remove the inclusion of linux/mdio-gpio.h in nas4220b, wbd111 and wbd222
boards since mdio-gpio is not used.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>