HID: uhid: Remove mutex_unlock while waiting

Because of recently introduced kernel change, previous change to
unlock mutex is not required as HID device addition is now done in
worker thread instead of main thread. Previous code flow was blocking
as uhid_hid_set_report was called from main thread which is not the
case now. Previous code flow was
uhid_char_write->uhid_dev_create2->uhid_hid_raw_request->
uhid_hid_set_report->__uhid_report_queue_and_wait->
wait_event_interruptible_timeout which is now changed to
uhid_char_write->uhid_dev_create2.

CRs-Fixed: 1112380
Signed-off-by: Hemant Gupta <hemantg@codeaurora.org>
Change-Id: I11c3e5628484739acc208deff84a82f34b1b7beb