ARM: ep93xx: vision_ep9307: Use MMC CD and RO GPIO

Pass the CD and RO GPIO numbers to the MMC SPI driver and remove the
custom .get_cd() and .get_ro() callback functions.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Chris Ball <cjb@laptop.org>