audio: Set 'maxOpenStreamCount' to unlimited for input ports

Since libaudiohal@aidl reports that the most current legacy C API
version is supported by the HAL, the audio server uses a different
logic for telephony scenarios than for the HIDL HAL. This involves
opening more streams on the same mix port. Allow opening
an unlimited number of streams. However, keep the number of active
streams to be `1`.

Bug: 302132812
Test: atest CtsMediaAudioTestCases --test-filter=".*AudioNativeTest.*"
Test: atest CtsMediaAudioTestCases --test-filter=".*CallAudioInterceptionTest.*"
Change-Id: I896398fca73f28d28d9397d00751394c969531b4