Revert "wl12xx: Change claiming of the SDIO bus"

This reverts commit 393fb560.

Commit b6ad726e ("mmc: core: Prevent too long response times
for suspend") fails the suspend if the mmc host can't be
claimed before suspend. As the host is claimed by us as long
as the chip is powered on, suspend will always fail.

Revert to claiming the sdio bus only when needed.

Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>