drm: Fix HDMI_STATIC_METADATA_TYPE1 constant

According to the CTA 861.G spec, HDMI_STATIC_METADATA_TYPE1 is
not 1, but zero, so fix this enum.

While this doesn't cause problems in the kernel yet, as the
constant isn't actively used by drivers yet, it did create
confusion while debugging HDR problems in yours truly, and
also potential bugs in userspace components, as the wrong
enum propagates to components, e.g., like it did already
into intel-gpu-tools (tests/kms_hdr.c) or is used as wrong
reference when writing future new userspace HDR components
like compositors.

Fixes: fbb5d035 ("drm: Add HDR source metadata property")
Signed-off-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Cc: Uma Shankar <uma.shankar@intel.com>
Cc: Shashank Sharma <shashank.sharma@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Simon Ser <contact@emersion.fr>
Signed-off-by: Simon Ser <contact@emersion.fr>
Link: https://patchwork.freedesktop.org/patch/msgid/20210124044010.18678-1-mario.kleiner.de@gmail.com

include/linux/hdmi.h

@@ -156,7 +156,7 @@ enum hdmi_content_type {
 };
 
 enum hdmi_metadata_type {
-	HDMI_STATIC_METADATA_TYPE1 = 1,
+	HDMI_STATIC_METADATA_TYPE1 = 0,
 };
 
 enum hdmi_eotf {