drm/i915: Perform dpll commit first, v2.

Warn for the wrong mask in enable only. Disable will have the wrong mask now
because the new state is committed before disabling the old state.

Changes since v1:
- Use crtc_mask (Durgadoss)
- Rebase.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1457944075-14123-3-git-send-email-maarten.lankhorst@linux.intel.com


Reviewed-by: Ander Conselvan de Oliveira <conselvan2@gmail.com>