usb: gadget: fsl_udc_core: Use module_platform_driver_probe macro

module_platform_driver_probe() eliminates the boilerplate and simplifies
the code.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Acked-by: Li Yang <leoli@freescale.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>