drm/i915: rip our vblank reset hacks for runtime PM

drm/i915: rip our vblank reset hacks for runtime PM

Now that we unconditionally dtrt when disabling/enabling crtcs we
don't need any hacks any longer to keep the vblank logic sane when
all the registers go poof. So let's rip it all out.

This essentially undoes

commit fe61358373e4bf9e796a564c4d2851c70ada10ff
Author: Paulo Zanoni <paulo.r.zanoni@intel.com>
Date:   Tue Jul 23 10:48:11 2013 -0300

    drm/i915: update last_vblank when disabling the power well

Apparently igt/kms_flip is already powerful enough to exercise this
properly, yay! See the reference regression report for details.

v2: Update testcase name

References: https://bugs.freedesktop.org/show_bug.cgi?id=66808
Testcase: igt/kms_flip/vblank-vs-*-rpm
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>