gpio: modify sysfs gpio export so that "value" displays as 0 or 1

gpiolib can export GPIOs to userspace via sysfs.  This patch modifies the
gpio_value_show() so that any non-zero value is explicitly printed as "1",
rather than whatever numerical value the lower-level driver returns.

Signed-off-by: Steve Falco <sfalco@harris.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>