mmc: mmc_spi: Remove platform data .get_cd() and .get_ro() callbacks

All platforms now pass the CD and RO GPIOs to the MMC SPI driver, those
callbacks are not used anymore. Remove them.

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