msm: vidc: Poll for idle_status bit prior to power collapse

During hardware suspend, host prepares video firmware for
power collapse before waiting for vcodec hardware to go
into idle state.Video firmware expects power collapse
command from host only after the vcodec hardware is
in idle state. Without this, video hardware continues
to process frame with host disabling the clocks.

The change waits for vcodec hardware to go into
idle state before preparing for power collapse.

Change-Id: Ie83c65cfe0bfbcccfcc6b58e0e67faa0d065fc0e
Signed-off-by: Santhosh Behara <santhoshbehara@codeaurora.org>