drm/i915: Plop vlv wm state into crtc_state

Relocate the vlv/chv wm state to live under intel_crtc_state. Note
that for now this just behaves as a temporary storage. But it'll be
easier to conver the thing over to properly pre-computing the state
when it's already in the right place.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170302171508.1666-5-ville.syrjala@linux.intel.com