HID: usbhid: free raw_report buffers in usbhid_stop

commit f7744fa16b96da57187dc8e5634152d3b63d72de upstream.

Free the unsent raw_report buffers when the device is removed.

Fixes a memory leak reported by syzbot at:
https://syzkaller.appspot.com/bug?id=7b4fa7cb1a7c2d3342a2a8a6c53371c8c418ab47



Reported-by:  <syzbot+47b26cd837ececfc666d@syzkaller.appspotmail.com>
Tested-by:  <syzbot+47b26cd837ececfc666d@syzkaller.appspotmail.com>
Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>