usb gadget: fix omap_udc DMA regression

This resolves another regression caused by the "use omap_read/write
instead of __REG" patch:  the hardware address used for DMA to/from
the UDC became wrong.  Bug noted by Russell King.

Reported-by: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>