drivers/gpio is platform-neutral

Update Kconfig and Makefile in drivers/gpio to discourage inappropriate
addition of platform-specific code.

[akpm@linux-foundation.org: fix tpyo]
Signed-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>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 724038d..7face91 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1,5 +1,5 @@
 #
-# GPIO infrastructure and expanders
+# platform-neutral GPIO infrastructure and expanders
 #
 
 config ARCH_WANT_OPTIONAL_GPIOLIB