USB: pxa2xx_udc: use generic gpio layer

This patch lets the pxa2xx_udc use the generic gpio layer,
on the relevant PXA and IXP systems.

Signed-off-by: Milan Svoboda <msvoboda@ra.rockwell.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>