usb: udc: lpc32xx: silence fall-through warning

Silence the following fall-through warning by adding a break statement:

drivers/usb/gadget/udc/lpc32xx_udc.c:2230:3: warning: this statement may
fall through [-Wimplicit-fallthrough=]

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>