audio: run ril_set_call_clock_sync() in stop_voice_session()

Some devices like the Samsung Galaxy S6, require this
to be run at the end of the voice session. However some
devices also need this to be run at the start of the
voice session whereas the S6 does not (see previous commit).

Change-Id: I833b57e262795fcbd8be6f44afb17b0f1ca6fee3
Signed-off-by: Usaamah Patel <ussyp2015@gmail.com>