drm/i915: Simplify error handling in intel_modeset_all_pipes()

No need for the extra break statements and whatnot, just return the
error directly. And tighten the scope of the local variables while at
it.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1479141311-11904-4-git-send-email-ville.syrjala@linux.intel.com


Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>