i965: Fix missing _NEW_SCISSOR in Broadwell SF_CLIP_VIEWPORT state.
The _Xmin/_Xmax/_Ymin/_Ymax values need to be guarded by _NEW_SCISSOR.
Fixes Piglit's scissor-many, and rendering in GNOME Shell.
Hopefully fixes similar issues with Unity and ChromeOS.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=75879
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Tested-by: James Ausmus <james.ausmus@intel.com>
Tested-by: Timo Aaltonen <tjaalton@ubuntu.com>