Revert "mmc: fix a race between card-detect rescan and clock-gate work instances"

This reverts commit 26fc8775, which has
been reported to cause boot/resume-time crashes for some users:

https://bbs.archlinux.org/viewtopic.php?id=118751

.

Signed-off-by: Chris Ball <cjb@laptop.org>
Cc: <stable@kernel.org>