HAL: Handle case 7 in derive_playback_snd_device

after SSR is triggered during playback on headset and
ringtone concurrency use-case, ringtone plays only on headset.
this use-case falls under case 7 which is not handled
by derive_playback_snd_device.

fix the issue by adding a condition to handle this use-case.

Change-Id: Ia8387de0591adb5ec864b1fce5af07620a9e2e3f