drm/kms: load fbcon from drm_kms_helper

Kconfig says fbcon is required by drm_kms_helper.  If radeon, fbcon,
and drm_kms_helper are all modules, radeon is auto loaded (by PCI id?),
drm_kms_helper is loaded because of the module dependency, but fbcon
isn't loaded leaving the console unusable.  Since fbcon is required
and there isn't an explicit module dependency, request the module
to be loaded from drm_kms_helper.

Signed-off-by: David Fries <david@fries.net>
Cc: David Airlie <airlied@linux.ie>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Dave Airlie <airlied@redhat.com>