Staging: emxx_udc: Switch to the gpio descriptor interface

Convert VBUS GPIO to use GPIO descriptors from <linux/gpio/consumer.h>
and stop using the old GPIO API.

Signed-off-by: Nishad Kamdar <nishadkamdar@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>