Audio: Fixed system/call stream volume can't adjust with HS connected.

Issue Description:
When headset connected, the system/voice call stream volume can't be
adjusted from Volume bar.

Root Cause:
Currently adjustStreamVolume is applied to stream type alias and the
device for the stream alias. So when headset connected and adjust
volume for SYSTEM_STREAM, the operation will be applied to RING_STREAM
(which is aliased by SYSTEM_STREAM) and speaker. As headset is returned
from getDeviceForStream(SYSTEM_STREAM), but speaker for RING_STREAM.

Solution:
Change the adjustStreamVolume to apply volume to the stream alias and
the device for the stream type exactly.

Change-Id: Icd226d9eb197017cd3c186a0096edaed755680ec
Signed-off-by: Guo Xie <gxie@marvell.com>