usb(4): Factor out the usb_check_request() function.
No functional change.
Sponsored by: NVIDIA Networking
Approved by: re (gjb)
(cherry picked from commit 8ed5bb59e913c61e61a4232e8221f35256f72ad2)
(cherry picked from commit 9157566d7ad58560c6fa0ba6c2b88587688ee02c)