mmc: core: host: only use wakelock for detect work

There is no need to take a wakelock for delayed lazy disable
work, it will be cancelled in the suspend handler and force
disabled.  Only take the wakelock when the detect work is
queued, and make sure to drop the wakelock if the work is
cancelled.

Change-Id: I1e507a5f98848954ea21d45e23b6192c3132a349
Signed-off-by: Colin Cross <ccross@android.com>