usb: gadget: udc: renesas_usb3: Use of_device_get_match_data() helper

Use the of_device_get_match_data() helper instead of open coding,
postponing the matching until when it's really needed.
Note that the renesas_usb3 driver is used with DT only, so there's
always a valid match.

Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>