audio policy: fix crash in findPreferredDevice() on duplicating outputs

Duplicating outputs do not have an associated IOProfile and
getPolicyAudioPort() returns null.

Add a method to AudioIODescriptorInterface to query if the
input or output descriptor corresponds to MMAP IO profile or not.

Bug: 153849965
Test: repro steps in the bug
Change-Id: I300356880198f1785e3a5e1359ffd393c6ae4190