audiopolicy: fix mix recorder regression

Engine is not only responsible of legacy remote submix for input
device selection (aka "0" adress) but also regular remote submix
with a given address. Filtering the remote submixes prevents engine
to select the remote submix for input stream in case a policy mix
rule has been set to record specific sources.

Bug: 130284799
Test: AudioPolicyEmulatorTests --gtest_filter=RecordInjectionSourceMatch/DynamicPolicyMixRecordInjectionTest

Change-Id: Iaafd1195b9ab5c82ad3bd2766061d982a10bb9da
Signed-off-by: Francois Gaffie <francois.gaffie@renault.com>