usb: gadget: rename CONFIG_USB_GADGET_PXA25X

Commit 193ab2a60700 ("usb: gadget: allow multiple gadgets to be built")
basically renamed the Kconfig symbol USB_GADGET_PXA25X to USB_PXA25X. It
did not rename the related macros in use at that time. Commit
c0a39151a405 ("ARM: pxa: fix inconsistent CONFIG_USB_PXA27X") did so for
all but one macro. Rename that last macro too now.

Fixes: 193ab2a60700 ("usb: gadget: allow multiple gadgets to be built")
Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>