audio: Clarify comments on AudioPortMixExt fields

Specify that '0' means 'unlimited' for
AudioPortMixExt.maxOpenStreamCount, and 'all opened streams'
for maxActiveStreamCount.

Bug: 205884982
Test: N/A
Merged-In: Ia212fef049778a85046e3333faa0ddf8fe167c1f
Change-Id: Ia212fef049778a85046e3333faa0ddf8fe167c1f
(cherry picked from commit 52ca76ed)

media/aidl/android/media/audio/common/AudioPortMixExt.aidl

@@ -32,12 +32,12 @@ parcelable AudioPortMixExt {
     AudioPortMixExtUseCase usecase;
     /**
      * Maximum number of input or output streams that can be simultaneously
-     * opened for this port.
+     * opened for this port. '0' means 'unlimited'.
      */
     int maxOpenStreamCount;
     /**
      * Maximum number of input or output streams that can be simultaneously
-     * active for this port.
+     * active for this port. '0' means 'all opened streams'.
      */
     int maxActiveStreamCount;
     /** Mute duration while changing device, when used for output. */