drm/i915/bdw: Add 42ms delay for IPS disable
drm/i915/bdw: Add 42ms delay for IPS disable

This is a requirement added to the spec. This patch will prevent
persistent corruption on the display.

v2: Make the wait before the vblank wait. (Art)
Try to finish early by polling the register
s/present/prevent (Chris)

Cc: Art Runyan <6775369b359967e3100dbadeab942952ddf3d34b@intel.com>
Signed-off-by: Ben Widawsky <73675debcd8a436be48ec22211dcf44fe0df0a64@bwidawsk.net>
[danvet: Upgrade debug output to ERROR.]
Signed-off-by: Daniel Vetter <c1b6782c4af8f0673da8923a0702a1832e5940f4@ffwll.ch>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs