accel/ivpu: Fix S3 system suspend when not idle

Wait for VPU to be idle in ivpu_pm_suspend_cb() before powering off
the device, so jobs are not lost and TDRs are not triggered after
resume.

Fixes: 852be13f

 ("accel/ivpu: Add PM support")
Signed-off-by: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Signed-off-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230331113603.2802515-3-stanislaw.gruszka@linux.intel.com