mmc: core: Fix broken clock gating with commit 9b0f5ecb

With commit 9b0f5ecb "mmc: Add support to handle Urgent
data transfer request" runtime MMC clock gating is broken.
The implementation in the commit introduces a new stop
transmission sequence due to which the underlying host
drivers may not always call mmc_request_done(). The clock
gating reference count must be updated in such cases failing
which the clocks are never turned off even when MMC is idle
for long time.

Change-Id: I226778ee98b3e967a2e7ee9a92b20d265e87d9e5
Signed-off-by: Sujit Reddy Thumma <sthumma@codeaurora.org>