mp_imgfmt: move DRMPRIME format to end of enum

dmabuf-wayland vo supports both DRMPRIME and VAAPI formats.
If upload filter is needed, we want to try VAAPI hwdec first
since most users will be using VAAPI, and there is a several second
delay when DRMPRIME hwdec is tried and fails.

video/img_format.h

@@ -276,7 +276,6 @@ enum mp_imgfmt {
     IMGFMT_DXVA2,           // IDirect3DSurface9 (NV12/P010/P016)
     IMGFMT_MMAL,            // MMAL_BUFFER_HEADER_T
     IMGFMT_MEDIACODEC,      // AVMediaCodecBuffer
-    IMGFMT_DRMPRIME,        // AVDRMFrameDescriptor
     IMGFMT_CUDA,            // CUDA Buffer
 
     // Not an actual format; base for mpv-specific descriptor table.
@@ -320,6 +319,7 @@ enum mp_imgfmt {
     IMGFMT_VAAPI,
     IMGFMT_VIDEOTOOLBOX,    // CVPixelBufferRef
     IMGFMT_VULKAN,          // VKImage
+    IMGFMT_DRMPRIME,        // AVDRMFrameDescriptor
 
     // Generic pass-through of AV_PIX_FMT_*. Used for formats which don't have
     // a corresponding IMGFMT_ value.