drm/i915: fix an error code in intel_modeset_all_tiles()

There is a cut and paste bug so we return the wrong error code.

Fixes: a603f5bd

 ("drm/i915/dp: Make sure all tiled connectors get added to the state with full modeset")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200107130322.gdk5b6jurifr26c2@kili.mountain