libcamera: pixelformats: include linux/drm_fourcc.h

Instead of having to include linux/drm_fourcc.h everywhere a DRM FourCC
is used in conjunction with PixelFormat include the header directly in
pixelformats.h.

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

include/libcamera/pixelformats.h

@@ -9,6 +9,8 @@
 
 #include <stdint.h>
 
+#include <linux/drm_fourcc.h>
+
 namespace libcamera {
 
 using PixelFormat = uint32_t;