i915: Emit 3DSTATE_SCISSOR_RECTANGLE_0 before 3DSTATE_SCISSOR_ENABLE

i915: Emit 3DSTATE_SCISSOR_RECTANGLE_0 before 3DSTATE_SCISSOR_ENABLE

According to gen2 BSpec the pipeline must be flushed at least up to the
windower before changing the scissor rect enable field. Emitting the
3DSTATE_SCISSOR_RECTANGLE_0 before 3DSTATE_SCISSOR_ENABLE is sufficient
to do that.

gen3 BSpec no longer has that piece of text, but let's make the same
change there too for symmetry. The spec does still say that the scissor
rectangle must be defined before enabling it, so the new order does seem
more in line with the spec.

Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>