mmc: queue: fix high power consumption

The cmdqd thread was marked as uninterruptible. This did not
allow the cmdqd thread to sleep when there is no traffic.
Added interruptible attributes to the thread.

Change-Id: I658eecabfff074044b23c7c270c9101a34d37a45
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>