These are fallback definitions in case libdrm is not new enough.
They are copied from libdrm 2.4.107.
struct hdr_output_metadata defines the contents of the blob to be used
with the connector property "HDR_OUTPUT_METADATA".
This is needed for programming a HDR mode in KMS.
This headers need to be excluded from Doxygen, because Doxygen chokes on
the kerneldoc markup.
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>