libcamera: Standardize on 'const auto'

'const auto' and 'auto const' are interchangeable in C++. There are 446
occurrences of the former in the code base, and 67 occurrences of the
latter. Standardize on the winner.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>

test/v4l2_videodevice/buffer_cache.cpp

@@ -133,7 +133,7 @@ public:
 		if (!cache.isEmpty())
 			return TestFail;
 
-		for (auto const &buffer : buffers) {
+		for (const auto &buffer : buffers) {
 			FrameBuffer &b = *buffer.get();
 			cache.get(b);
 		}