drm/udl: Use drm_fb_helper_fill_info

This should not result in any changes.

v2: Rebase

v3: Don't forget to remove the info->par assignment (Noralf)

Acked-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Sean Paul <sean@poorly.run>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Emil Lundmark <lndmrk@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190326132008.11781-19-daniel.vetter@ffwll.ch