USB: pxa2xx_udc understands GPIO based VBUS sensing

This updates the PXA 25x UDC board-independent infrastructure for VBUS sensing
and the D+ pullup.  The original code evolved from rather bizarre support on
Intel's "Lubbock" reference hardware, so that on more sensible hardware it
doesn't work as well as it could/should.

The change is just to teach the UDC driver how to use built-in PXA GPIO pins
directly.  This reduces the amount of board-specfic object code needed, and
enables the use of a VBUS sensing IRQ on boards (like Gumstix) that have one.
With VBUS sensing, the UDC is unclocked until a host is actually connected.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>