wm8994: clean up of audio files.

Change-Id: I10326e6ac0c3419021664ad9a62289a882fe3341
wm8994:  Bring back pm_runtime

-Fix up issues with pm_runtime
-Added in check to ensure wm8958 regulator doesn't try and
 disable if already disabled

Change-Id: Ic681eebe82a587d1c5ae9d27ccb95f9065ccccbe