drm/i915: Use new atomic iterator macros in wm code

drm/i915: Use new atomic iterator macros in wm code

The watermark code needs to look at the new allocations, so use
for_each_new_crtc_in_state everywhere.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1489071125-917-4-git-send-email-maarten.lankhorst@linux.intel.com
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>