msm: pil-q6v3: Move to prepare()/unprepare() clock APIs

The clock driver is moving to prepare/unprepare apis. Make sure
to call prepare/unprepare in non-atomic context, therefore
replace the timer with a workqueue and call the combined
prepare/enable apis appropriately.

Change-Id: Ib2616a9dcb8b88cdf59e72e72d79f584aca80210
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>