drm/i915: Fix noatomic crtc disabling, v2.

drm/i915: Fix noatomic crtc disabling, v2.

This fixes the breakage caused by

commit a6bd4e74986245e86051dbe176254a7e3a0be724
Author: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Date:   Mon Jun 15 12:33:53 2015 +0200

    drm/i915: Update less state during modeset.

    No need to repeatedly call update_watermarks, or update_fbc.
    Down to a single call to update_watermarks in .crtc_enable

    Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
    Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
    Tested-by(IVB): Matt Roper <matthew.d.roper@intel.com>
    Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Add missing shared dpll disable to the noatomic disable function.

This function will be replaced by its atomic counterpart soon.

Changes since v1:
- intel_crtc->active and watermarks are fixed by a patch from
  Patrik Jakobsson

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>