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/qcam/dng_writer.cpp

@@ -215,7 +215,7 @@ void packScanlineIPU3(void *output, const void *input, unsigned int width)
 	}
 }
 
-void thumbScanlineIPU3(const FormatInfo &info, void *output,
+void thumbScanlineIPU3([[maybe_unused]] const FormatInfo &info, void *output,
 		       const void *input, unsigned int width,
 		       unsigned int stride)
 {
@@ -350,7 +350,8 @@ static const std::map<PixelFormat, FormatInfo> formatInfo = {
 int DNGWriter::write(const char *filename, const Camera *camera,
 		     const StreamConfiguration &config,
 		     const ControlList &metadata,
-		     const FrameBuffer *buffer, const void *data)
+		     [[maybe_unused]] const FrameBuffer *buffer,
+		     const void *data)
 {
 	const auto it = formatInfo.find(config.pixelFormat);
 	if (it == formatInfo.cend()) {

src/qcam/main.cpp

@@ -17,7 +17,7 @@
 #include "../cam/stream_options.h"
 #include "main_window.h"
 
-void signalHandler(int signal)
+void signalHandler([[maybe_unused]] int signal)
 {
 	qInfo() << "Exiting";
 	qApp->quit();

src/qcam/main_window.cpp

@@ -637,7 +637,8 @@ void MainWindow::captureRaw()
 	captureRaw_ = true;
 }
 
-void MainWindow::processRaw(FrameBuffer *buffer, const ControlList &metadata)
+void MainWindow::processRaw(FrameBuffer *buffer,
+			    [[maybe_unused]] const ControlList &metadata)
 {
 #ifdef HAVE_DNG
 	QString defaultPath = QStandardPaths::writableLocation(QStandardPaths::PicturesLocation);