drm/amdgpu: replace drm_detect_hdmi_monitor() with drm_display_info.is_hdmi

Once EDID is parsed, the monitor HDMI support information is available
through drm_display_info.is_hdmi. The amdgpu driver still calls
drm_detect_hdmi_monitor() to retrieve the same information, which
is less efficient. Change to drm_display_info.is_hdmi

This is a TODO task in Documentation/gpu/todo.rst

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Claudio Suarez <cssk@net-c.es>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>