sh: sh7757: Fix GPIO_FN_ET0_MDIO and GPIO_FN_ET1_MDIO GPIO entries

The GPIO_FN_ET0_MDIO and GPIO_FN_ET1_MDIO GPIO entries incorrectly
reference the ET0_MDC_MARK and ET1_MDC_MARK marks instead of the
ET0_MDIO_MARK and ET1_MDIO_MARK marks. Fix them.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>