usb: gadget: udc: atmel: update endpoint allocation for sam9x60

The DPRAM memory from the USB High Speed Device Port (UDPHS) hardware
block was increased. This patch updates the endpoint allocation for sam9x60
to take advantage of this larger memory. At the same time the
constraint to allocate the endpoints in order was lifted. To handle old
and new hardware in the same driver the ep_prealloc was added.

Signed-off-by: Cristian Birsan <cristian.birsan@microchip.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>