drm/i915: split enable/disable vblank code into chipset specific functions

This makes the Ironlake+ code trivial and generally simplifies things.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Keith Packard <keithp@keithp.com>
3 files changed