On Broadwell, any PIPE_CONTROL with the "State Cache Invalidate" bit set
must be preceded by a PIPE_CONTROL with the "CS Stall" bit set.

Documented on the BSpec 3D workarounds page.
Reviewed-by: NRafael Barbalho <rafael.barbalho@intel.com>
Signed-off-by: NKenneth Graunke <kenneth@whitecape.org>
[vsyrjala: add chv w/a note too]
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>