ALSA: hda/tas2781: restore power state after system_resume

After system_resume the amplifers will remain off, even if they were on
before system_suspend.

Use playback_started bool to save the playback state, and restore power
state based on it.

Fixes: 5be27f1e ("ALSA: hda/tas2781: Add tas2781 HDA driver")
Signed-off-by: Gergo Koteles <soyer@irl.hu>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Message-ID: <1742b61901781826f6e6212ffe1d21af542d134a.1709918447.git.soyer@irl.hu>