mmc: core: Fix mmc shutdown issue

In a specific case for poweroff notify host resumes the card in
order to shut it down properly. During resume if the mmc device is
not suspended it returns with a default error -22 though there is
no error. Set that default error value as zero and make changes
to be consistent with the code flow.

Change-Id: Iff46bc8c517009b9d4348f8979f6c7e31639de84
Signed-off-by: Sarthak Garg <sartgarg@codeaurora.org>