meson: Remove -Wno-unused-parameter

We build libcamera with -Wno-unused-parameter and this doesn't cause
much issue internally. However, it prevents catching unused parameters
in inline functions defined in public headers. This can lead to
compilation warnings for applications compiled without
-Wno-unused-parameter.

To catch those issues, remove -Wno-unused-parameter and fix all the
related warnings with [[maybe_unused]].

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

src/android/camera_device.cpp

@@ -1548,8 +1548,9 @@ void CameraDevice::notifyError(uint32_t frameNumber, camera3_stream_t *stream)
 /*
  * Produce a set of fixed result metadata.
  */
-std::unique_ptr<CameraMetadata> CameraDevice::getResultMetadata(int frame_number,
-								int64_t timestamp)
+std::unique_ptr<CameraMetadata>
+CameraDevice::getResultMetadata([[maybe_unused]] int frame_number,
+				int64_t timestamp)
 {
 	/*
 	 * \todo Keep this in sync with the actual number of entries.