Merge "libeffects: Add multichannel support to Reverb" am: ba88b6bfd1 am: 6a715cf983 am: a364a910cf

Original change: https://android-review.googlesource.com/c/platform/frameworks/av/+/1396509

Change-Id: Id136c4cf65c9623eca5d017dc7fe21231e4449c2