ixp4xx: fix compilation by adding gpiolib support

commit 9dde0ae3769875ec1370cb316e50c54b57d52c1a upstream.

Once again, ixp4xx no longer even compiles. This patch fixes the issue
by converting over to gpiolib. This patch was first made by Imre and
posted by Marc, and I added in Russell's suggestion to empty the gpio
header file.

This fix should also go for 3.1, 3.2, 3.3, and 3.4.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>