i9300: audio: fix input device selection

http://review.cyanogenmod.org/61104 broke input device
selection resulting in single channel audio for recordings.

Change-Id: I58d5a0997b22cfe5489030e698e83d1768161132
(cherry picked from commit 0b9ef7aee815199079350c8767b8c31482a05c20)
i9300: audio: bring back removed microphone fix

http://review.cyanogenmod.org/61104 has reverted http://review.cyanogenmod.org/51085
which has bought back issues with microphone after a voice call. After a voice call,
the microphone is either not working or the recorded audio is very faint and not
audible.

The Input device has to be explicitly set to AUDIO_DEVICE_NONE after a voice call,
since force_all_standby() wouldn't work for a voice call usecase.

More details about the fix is included in the gerrit comments for the actual patch.

Change-Id: I87c63b0ec4390ec3e5703e1de5804c10289ee423