Convert mask types from uint32_t to enum type

This applies to the following types:

- audio_gain_mode_t;
- audio_flags_mask_t;
- audio_channel_representation_t;
- audio_channel_mask_t;
- audio_devices_t.

Enum types are distinct thus proper overloading on the type
is possible in C++. Also, assignments to enum types are
less prone to errors.

Bug: 169889714
Test: basic audio functionality
      m stagefright
      atest audiopolicy_tests
Change-Id: I42506484b1d0b0482618b7314fad4c8012a06fb4
diff --git a/services/audiopolicy/engineconfigurable/src/InputSource.cpp b/services/audiopolicy/engineconfigurable/src/InputSource.cpp
index aa06ae3..f4645e6 100644
--- a/services/audiopolicy/engineconfigurable/src/InputSource.cpp
+++ b/services/audiopolicy/engineconfigurable/src/InputSource.cpp
@@ -51,7 +51,7 @@
         mApplicableDevices = devices;
         return NO_ERROR;
     }
-    devices |= AUDIO_DEVICE_BIT_IN;
+    devices = static_cast<audio_devices_t>(devices | AUDIO_DEVICE_BIT_IN);
     if (!audio_is_input_device(devices)) {
         ALOGE("%s: trying to set an invalid device 0x%X for input source %s",
               __FUNCTION__, devices, getName().c_str());