drm/amd/display: Fix incorrect comment

Fix incorrect comment about hardware capabilities debugfs interface.

Reviewed-by: Jerry Zuo <jerry.zuo@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>