m7-common: ignore firmware partitions in recovery

This removes /firmware/mdm and /firmware/q6 from the listed partitions
in the Mounts and Storage menu.

Change-Id: I7154018b6238d6e17bdabb02ce9b4e4225595b15
m7: Fix remote submix sample rate

 * Avoid mismatch between source and sink.

Change-Id: I1ec9b7a723e21ccad7bbd8d23d794d099d8afc38
Various code and structure cleanup

-- update tree for "m7" build
-- remove unused prebuilts