Revert "m4: remove audioamp temporarily"

This reverts commit 6ebf5e14952b9fe176ae9f1f50b65640a7fa31f6.

Change-Id: I8b126c8e1615b60bea0782fe3f76c446a4e16567
m4: libaudioamp: Add initialization function stubs

Change-Id: I34aad7e268dbb59edb0d6c224f5f95cc75e405fa
m4: tfa9887: Fix race in checking whether or not to reconfigure

Multiple threads can request that we set_mode.  When
we check to see if we need to reconfigure the amp, make sure
that we are locked to avoid race conditions.

Change-Id: Ic247fdd8d1c55cd054053b9b7dc38d99a16cb33f
m4: tfa9887: Fix both speakers playing right channel

There was a little typo in the code that made left channel
not being played at all and right channel being played through two speakers.

Change-Id: I1f0328c77540df9cc075967ddac85d9598c91c5d
m4: Use custom libaudioamp

Change-Id: I04147700e5a2291d817799fe6cb22fcf817217d4
Merge remote-tracking branch 'cm/cm-11.0' into HEAD