USB: atmel uaba: Adding invert vbus_pin

Adding vbus_pin_inverted so that the usb detect pin can be active high
or low depending on HW implementation also replaced the
gpio_get_value(udc->vbus_pin); with a call to vbus_is_present(udc); This
allows the driver to be loaded and save about 0,15W on the consumption.

Signed-off-by: Eirik Aanonsen <eaa@wprmedical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>