mmc: mmc_spi: Support CD/RO GPIOs

Add support for passing CD/RO GPIO numbers directly to the mmc_spi
driver instead of relying solely on board code callbacks to retrieve the
CD/RO signals values. The driver will enable debouncing on the card
detect GPIO if the cd_debounce field is set to a non-zero value.

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>