ASoC: SOF: pci: mark last_busy value at runtime PM init

ASoC: SOF: pci: mark last_busy value at runtime PM init

If last_busy value is not set at runtime PM enable, the device will be
suspend immediately after usage counter is 0. Set the last_busy value to
make sure delay is working at first boot up.

Signed-off-by: Pan Xiuli <xiuli.pan@linux.intel.com>
Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20190722141402.7194-2-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>