MdeModulePkg/SdMmc: update TPL to notify to fix UEFI SCT hang

We have to upgrade the TPL level used by SdMmc stack because the
following flow:

DiskIo2ReadWriteDisk() in logical partition -> PartitionReadBlocksEx()
in logical partition at TPL callback level -> ProbeMediaStatusEx()
with sync request -> DiskIo2ReadWriteDisk() in physical partition ->
 waiting for async task completion.

if the low layer driver doesn't run at TPL_NOTIFY level, it will have
no time to trigger async task and cause system hang.

Cc: Hao Wu <hao.a.wu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Feng Tian <feng.tian@intel.com>
Reviewed-by: Hao Wu <hao.a.wu@intel.com>

MdeModulePkg/Bus/Sd/SdDxe/SdDxe.c

@@ -800,7 +800,7 @@ SdDxeDriverBindingStop (
     //
     // Free all on-going async tasks.
     //
-    OldTpl = gBS->RaiseTPL (TPL_CALLBACK);
+    OldTpl = gBS->RaiseTPL (TPL_NOTIFY);
     for (Link = GetFirstNode (&Device->Queue);
          !IsNull (&Device->Queue, Link);
          Link = NextLink) {