usb: gadget: zynq: Fix usb ethernet gadget probe error

This patch is based on the below commit
"usb: gadget: add "maxpacket_limit" field to struct usb_ep"
(sha1:e117e742)

Value of "maxpacket_limit" should be set in UDC driver probe function, using
usb_ep_set_maxpacket_limit() function, defined in gadget.h. This function
set choosen value to both "maxpacket_limit" and "maxpacket" fields.

Signed-off-by: Punnaiah Choudary Kalluri <punnaia@xilinx.com>
Tested-by: Nathan Rossi <nathan.rossi@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>