i965/skl: Set the pulls bary bit in 3DSTATE_PS_EXTRA

i965/skl: Set the pulls bary bit in 3DSTATE_PS_EXTRA

On Gen9+ there is a new bit in 3DSTATE_PS_EXTRA that must be set if
the shader sends a message to the pixel interpolator. This fixes the
interpolateAt* tests on SKL, apart from interpolateatsample-nonconst
but that is not implemented anywhere so it's not a regression.

Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Cc: "10.6 10.5" <mesa-stable@lists.freedesktop.org>