Revert "mmc: core: Hold a wake lock accross delayed work + mmc rescan"

This reverts commit c4cda98f ("mmc: core: Hold a wake lock
accross delayed work + mmc rescan")

The old wakelock implementation for the mmc subsystem has been
reworked using the pm framework in commit bbd43682
("mmc: core: Signal wakeup event at card insert/removal")

It's no longer required, hence reverting this change and leftovers
of extend wakelock that is also not required.

Change-Id: I1c99e6e04fab8cdbdba6c77c87230137d05cef27
Signed-off-by: Venkat Gopalakrishnan <venkatg@codeaurora.org>