PCMCIA: soc_common: add GPIO support for card status signals

Add GPIO support for reading the card status (card detect, ready,
battery voltage detect) signals into soc_common code.  As we want
interrupts from these GPIOs, this takes over the old irq handling
infrastructure for card status signals, which will now be managed
entirely by the soc_common code.

Acked-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>