drm/i915/fbdev: Actually configure untiled displays

If we skipped all the connectors that were not part of a tile, we would
leave conn_seq=0 and conn_configured=0, convincing ourselves that we
had stagnated in our configuration attempts. Avoid this situation by
starting conn_seq=ALL_CONNECTORS, and repeating until we find no more
connectors to configure.

Fixes: 754a7659 ("drm/i915/fbdev: Stop repeating tile configuration on stagnation")
Reported-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190215123019.32283-1-chris@chris-wilson.co.uk
Cc: <stable@vger.kernel.org> # v3.19+