drm/amd/display: Update MST edid property every time

Extended fix to: "Don't read EDID in atomic_check"

Fix display property not observed in GUI display after hot plug.

Call drm_mode_connector_update_edid_property every time in
.get_modes hook, due to the fact that edid property is getting
removed from usermode ioctl DRM_IOCTL_MODE_GETCONNECTOR each time
in hot unplug.

Signed-off-by: Jerry (Fangzhi) Zuo <Jerry.Zuo@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org