drm/amdgpu: update drm_display_info correctly when the edid is read

drm_display_info is updated by drm_get_edid() or
drm_connector_update_edid_property(). In the amdgpu driver it is almost
always updated when the edid is read in amdgpu_connector_get_edid(),
but not always.  Change amdgpu_connector_get_edid() and
amdgpu_connector_free_edid() to keep drm_display_info updated.

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>