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/device3/Camera3OutputStream.cpp b/services/camera/libcameraservice/device3/Camera3OutputStream.cpp
index 396104c..3035aa5 100644
--- a/services/camera/libcameraservice/device3/Camera3OutputStream.cpp
+++ b/services/camera/libcameraservice/device3/Camera3OutputStream.cpp
@@ -393,13 +393,12 @@
             const camera_stream_buffer &buffer,
             nsecs_t timestamp,
             nsecs_t readoutTimestamp,
-            bool output,
+            [[maybe_unused]] bool output,
             int32_t transform,
             const std::vector<size_t>& surface_ids,
             /*out*/
             sp<Fence> *releaseFenceOut) {
 
-    (void)output;
     ALOG_ASSERT(output, "Expected output to be true");
 
     status_t res;
@@ -522,8 +521,7 @@
     return res;
 }
 
-void Camera3OutputStream::dump(int fd, const Vector<String16> &args) const {
-    (void) args;
+void Camera3OutputStream::dump(int fd, [[maybe_unused]] const Vector<String16> &args) const {
     String8 lines;
     lines.appendFormat("    Stream[%d]: Output\n", mId);
     lines.appendFormat("      Consumer name: %s\n", mConsumerName.string());