drm/i915: Take modeset locks around intel_modeset_setup_hw_state()

Some lower level things get angry if we don't have modeset locks
during intel_modeset_setup_hw_state(). Actually the resume and
lid_notify codepaths alreday hold the locks, but the init codepath
doesn't, so fix that.

Note: This slipped through since we only disable pipes if the
plane/pipe linking doesn't match. Which is only relevant on older
gen3 mobile machines, if the BIOS fails to set up our preferred
linking.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: stable@vger.kernel.org
Tested-and-reported-by: Paul Bolle <pebolle@tiscali.nl>
[danvet: Add note now that I could confirm my theory with the log
files Paul Bolle provided.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>