drm/i915: remove Pineview EOS protection support

HW guys have an evaluation about the impact about EOS, and say the impact
is quite small, so they have removed EOS detection support. This patch
removes EOS feature.

revert commit 04302965
directly reverting it gives a hunk error, so please use this one.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
[anholt: fixed up commit message for update that the feature's really gone]