Code clean for libcameraservice

Cleaning compile warnings "variable 'XX' set but not used":
1. Remove the variables which are obviously not used;
2. Add "[[maybe_unused]]" to variable declaration of the ones
   which are potentially used.

For the unused function parameters which were cast by "(void)":
We have changed them to the C++17 attribute "[[maybe_unused]]".
This seems not that necessary but it avoids redundant code lines.

Test: mmm frameworks/av/services/camera/libcameraservice,
      presubmit check.

Change-Id: Ia68b78c01f8254d76be81b1ce98d2a5c3d7eea46
Signed-off-by: Jing Mike <jingyangliu@eswincomputing.com>
diff --git a/services/camera/libcameraservice/api2/CameraDeviceClient.cpp b/services/camera/libcameraservice/api2/CameraDeviceClient.cpp
index bc76397..202599b 100644
--- a/services/camera/libcameraservice/api2/CameraDeviceClient.cpp
+++ b/services/camera/libcameraservice/api2/CameraDeviceClient.cpp
@@ -61,7 +61,7 @@
         bool systemNativeClient,
         const std::optional<String16>& clientFeatureId,
         const String8& cameraId,
-        int api1CameraId,
+        [[maybe_unused]] int api1CameraId,
         int cameraFacing,
         int sensorOrientation,
         int clientPid,
@@ -81,8 +81,6 @@
             servicePid,
             overrideToPortrait),
     mRemoteCallback(remoteCallback) {
-    // We don't need it for API2 clients, but Camera2ClientBase requires it.
-    (void) api1CameraId;
 }
 
 // Interface used by CameraService