usb: gadget: udc: atmel: Remove unnecessary macros

commit 46ddd79e ("usb: gadget: udc: atmel: Remove AVR32 bits from the
driver") left the accessor macros introduced by commit a3dd3bef

 ("usb:
gadget: atmel_usba: use endian agnostic IO on ARM"). They can now be
removed.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>