usb: gadget: dummy_hcd: clean up checkpatch

This patch converts checkpatch output of
|./scripts/checkpatch.pl drivers/usb/gadget/dummy_hcd.c -file

from
|total: 22 errors, 174 warnings, 2642 lines checked

to
|total: 0 errors, 0 warnings, 2632 lines checked
Signed-off-by: NSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: NFelipe Balbi <balbi@ti.com>