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/Camera3InputStream.cpp b/services/camera/libcameraservice/device3/Camera3InputStream.cpp
index 9a3f7ed..631bb43 100644
--- a/services/camera/libcameraservice/device3/Camera3InputStream.cpp
+++ b/services/camera/libcameraservice/device3/Camera3InputStream.cpp
@@ -104,17 +104,14 @@
 
 status_t Camera3InputStream::returnBufferCheckedLocked(
             const camera_stream_buffer &buffer,
-            nsecs_t timestamp,
-            nsecs_t readoutTimestamp,
-            bool output,
+            [[maybe_unused]] nsecs_t timestamp,
+            [[maybe_unused]] nsecs_t readoutTimestamp,
+            [[maybe_unused]] bool output,
             int32_t /*transform*/,
             const std::vector<size_t>&,
             /*out*/
             sp<Fence> *releaseFenceOut) {
 
-    (void)timestamp;
-    (void)readoutTimestamp;
-    (void)output;
     ALOG_ASSERT(!output, "Expected output to be false");
 
     status_t res;
@@ -218,8 +215,7 @@
     return OK;
 }
 
-void Camera3InputStream::dump(int fd, const Vector<String16> &args) const {
-    (void) args;
+void Camera3InputStream::dump(int fd, [[maybe_unused]] const Vector<String16> &args) const {
     String8 lines;
     lines.appendFormat("    Stream[%d]: Input\n", mId);
     write(fd, lines.string(), lines.size());