mmc: sdhci: pxav3: Delete GPIO handling

The platform data for the PXAv3 driver allows passing a card
detect GPIO, but this code is not used in the kernel.

In order to not encourage the use of the old global GPIO
numberspace we need to remove this.

Card detect (and write protect) GPIO can easily be added into
the driver using machine descriptor tables instead, and the
descriptor-based (gpiod) variants of the slot GPIO APIs.

Cc: Jisheng Zhang <jszhang@marvell.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>