usb: gadget: uvc: fix list double add in uvcg_video_pump

In the Linux kernel, the following vulnerability has been resolved:

usb: gadget: uvc: fix list double add in uvcg_video_pump

A panic can occur if the endpoint becomes disabled and the

uvcg_video_pump adds the request back to the req_free list after it has

already been queued to the endpoint. The endpoint complete will add the

request back to the req_free list. Invalidate the local request handle

once it's been queued.

<6>[ 246.796704][T13726] configfs-gadget gadget: uvc: uvc_function_set_alt(1, 0)

<3>[ 246.797078][ T26] list_add double add: new=ffffff878bee5c40, prev=ffffff878bee5c40, next=ffffff878b0f0a90.

<6>[ 246.797213][ T26] ------------[ cut here ]------------

<2>[ 246.797224][ T26] kernel BUG at lib/list_debug.c:31!

<6>[ 246.807073][ T26] Call trace:

<6>[ 246.807180][ T26] uvcg_video_pump+0x364/0x38c

<6>[ 246.807366][ T26] process_one_work+0x2a4/0x544

<6>[ 246.807394][ T26] worker_thread+0x350/0x784

<6>[ 246.807442][ T26] kthread+0x2ac/0x320