gpiolib support for the PXA architecture

This adds gpiolib support for the PXA architecture:
  - move all GPIO API functions from generic.c into gpio.c
  - convert the gpio_get/set_value macros into inline functions

This makes it easier to hook up GPIOs provided by external chips like
ASICs and CPLDs.

Signed-off-by: Philipp Zabel <philipp.zabel@gmail.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Jean Delvare <khali@linux-fr.org>
Cc: Eric Miao <eric.miao@marvell.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Ben Gardner <bgardner@wabtec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
[ Minor ARM fixup from David Brownell folded into this ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>