i965/vs: Move uses of brw_compile from do_vs_prog to brw_vs_emit.

i965/vs: Move uses of brw_compile from do_vs_prog to brw_vs_emit.

The brw_compile structure is closely tied to the Gen4-7 hardware
encoding.  However, do_vs_prog is very generic: it just calls out to
get a compiled program and then uploads it.

This isn't ultimately where we want it, but it's a step in the right
direction: it's now closer to the code generator.

Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>