libcamera: stream: add initial StreamConfiguration structure

Add an initial StreamConfiguration implementation to hold configuration
data for a single stream of a Camera. In its current form not many
configuration parameters are supported but it's expected the number of
options will grow over time.

At this stage the pixel format is represented as an unsigned int to
allow for easy mapping to the V4L2 API. This might be subject to change
in the future as we finalize how libcamera shall represent pixel
formats.

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

include/libcamera/stream.h

@@ -13,6 +13,12 @@ class Stream final
 {
 };
 
+struct StreamConfiguration {
+	unsigned int width;
+	unsigned int height;
+	unsigned int pixelFormat;
+};
+
 } /* namespace libcamera */
 
 #endif /* __LIBCAMERA_STREAM_H__ */