drm/edid: Fix docbook in drm_hdmi_infoframe_set_hdr_metadata()

Fixes the following warnings:
../drivers/gpu/drm/drm_edid.c:4925: warning: Function parameter or member 'conn_state' not described in 'drm_hdmi_infoframe_set_hdr_metadata'
../drivers/gpu/drm/drm_edid.c:4925: warning: Excess function parameter 'hdr_metadata' description in 'drm_hdmi_infoframe_set_hdr_metadata'

Fixes: 2cdbfd66 ("drm: Enable HDR infoframe support")
Cc: Uma Shankar <uma.shankar@intel.com>
Cc: Shashank Sharma <shashank.sharma@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: Hans Verkuil <hansverk@cisco.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-fbdev@vger.kernel.org
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190523135504.184354-1-sean@poorly.run