usb: gadget: at91: fix the number of endpoint parameter

usb: gadget: at91: fix the number of endpoint parameter

In sama5d3 SoC, there are 16 endpoints, which is different with
earlier SoCs (only have 7 endpoints). The USBA_NR_ENDPOINTS macro
is not suitable for sama5d3. So, get the endpoints number through
the udc->num_ep, which get from platform data for non-dt kernel,
or parse from dt node.

Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>