mmc: queue: Fix queue_lock spinlock bug from CMDQ shutdown path

CMDQ shutdown path calls blk_cleanup_queue, which changes queue_lock
from driver lock to it's original request_queue lock.
Hence during above shutdown process if below sequence is exercised
as well then may see below spinlock bug.

a) Some process say iozoneA has already acquired queue_lock (which
   is md->lock).
b) adb reboot has been issued and CMDQ driver has completed calling
   blk_cleanup_queue which switches the queue_lock from md->lock to
   q->__queue_lock.
c) ProcessA tries to release queue_lock but finds an unbalance that
   the lock is already released

Hence remove blk_cleanup_queue and instead make sure there are no
active_reqs in flight by mmccmdqd before this kthread is exited.

Callstack:
<6> BUG: spinlock already unlocked on CPU#6, iozone/4391
<6> lock: 0xffffffc06ab8be80, .magic: dead4ead,
.owner: <none>/-1, .owner_cpu: -1
[ffffffc0420e3b28] __delay at ffffffc00031a328
[ffffffc0420e3b38] __const_udelay at ffffffc00031a304
[ffffffc0420e3b58] msm_trigger_wdog_bite at ffffffc0004476cc
[ffffffc0420e3b68] spin_bug at ffffffc0000e4554
[ffffffc0420e3b98] do_raw_spin_unlock at ffffffc0000e47a0
[ffffffc0420e3bc8] _raw_spin_unlock_irq at ffffffc000db3ee0
[ffffffc0420e3be8] blk_queue_bio at ffffffc0002ff1e4
[ffffffc0420e3bf8] generic_make_request at ffffffc0002fd210
[ffffffc0420e3c58] submit_bio at ffffffc0002fd328
[ffffffc0420e3ca8] submit_bio_wait at ffffffc0002f5768
[ffffffc0420e3d00] compat_sys_call_table at ffffffc00008e000
[ffffffc0420e3d18] submit_bio_wait at ffffffc0002f574c
[ffffffc0420e3d38] __blkdev_issue_flush at ffffffc00030043c
[ffffffc0420e3da8] blkdev_issue_flush at ffffffc000300494
[ffffffc0420e3dd8] ext4_sync_fs at ffffffc0002597a4

CRs-fixed: 953541
Change-Id: I769cc25c14b6d873f64a898d6b73f33cc59d9c5d
Signed-off-by: Ritesh Harjani <riteshh@codeaurora.org>
[xiaonian@codeaurora.org: fixed trivial merge conflicts]
Signed-off-by: Xiaonian Wang <xiaonian@codeaurora.org>