audio: fix left and right speaker inversion

Fixed the following issues in mixer_paths.xml:
- Left/Right speaker inversion:
left is on LINEOUT2 and right is on LINEOUT1.
- Defined "handset" path as "speaker" path as there is no earpiece.
Ideally audio_policy.conf should not report earpiece device and the QCOM
audio HAL should be configurable for the types of devices supported.
- Removed mapping of RX6 and RX7 SLIMbus channels as there is no
baseband audio connection.

Bug: 8698713

Change-Id: Ib88bbfe1af8ede94729cd4215f54739331019296
1 file changed