i965: Remove two_side_color from brw_compute_vue_map().

i965: Remove two_side_color from brw_compute_vue_map().

Since we now lay out the VUE the same way regardless of whether
two-sided color is enabled, brw_compute_vue_map() no longer needs to
know whether two-sided color is enabled.  This allows the two-sided
color flag to be removed from the clip, GS, and VS keys, so that fewer
GPU programs need to be recompiled when turning two-sided color on and
off.

Reviewed-by: Eric Anholt <eric@anholt.net>