drm/i915: Implement Wa_1607090982

SIMD16 with Src0 scalar might conflict between Src1/Src2 and cause
GRF read issue. Workaround this issue by setting bit 14 in 0xe4f4
which will disable early read/src swap of Src0.

Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200207155138.30978-2-mika.kuoppala@linux.intel.com