gpiolib: update Documentation/gpio.txt
gpiolib: update Documentation/gpio.txt

Update Documentation/gpio.txt, primarily to include the new "gpiolib"
infrastructure.

Signed-off-by: David Brownell <a0d09457d62acbdeb1fae1223575100ccbfffdf9@users.sourceforge.net>
Cc: Jean Delvare <49ad6a9f5aa17024c23048df346d55bda6837e01@linux-fr.org>
Cc: Eric Miao <e9e0335ae43eee51396737d09983d9b25d00e51e@marvell.com>
Cc: Sam Ravnborg <f16bed56189e249fe4ca8ed10a1ecae60e8ceac0@ravnborg.org>
Cc: Haavard Skinnemoen <de7418319212d7eab32260a76732c1f83e514852@atmel.com>
Cc: Philipp Zabel <1f94b3da04d839c1c06fd881f52fcf8011297561@gmail.com>
Cc: Russell King <c2093e01fa868776d7876ac617ce6d2ac30cb904@arm.linux.org.uk>
Cc: Ben Gardner <57a789cf15db64f2607c0c3b087a795328c26804@wabtec.com>
Signed-off-by: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Signed-off-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs