drm/i915/cnl: WaDisableEnhancedSBEVertexCaching

WA forTDS handle reallocation getting dropped by SDE,
which may result in PS attribute corruption.

Disable enhanced SBE vertex caching in COMMON_SLICE_CHICKEN2 offset.

v2: Make it until B0 as spec tells. (by Mika).

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Oscar Mateo <oscar.mateo@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170815231651.975-3-rodrigo.vivi@intel.com