drm/udl: Set VGA connector

Set the connector type to VGA. The previously exported DVII type
isn't even supported by the driver.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220208143152.5846-1-tzimmermann@suse.de