i965: Factor out push locations.

With UBOs, the answer of "have we decided to push this uniform" gets
a bit more complicated - for one, we have multiple surfaces.  This
patch refactors things so we can add the new code in a single place.

Reviewed-by: Matt Turner <mattst88@gmail.com>

src/intel/compiler/brw_fs.h

@@ -125,6 +125,8 @@ public:
    void split_virtual_grfs();
    bool compact_virtual_grfs();
    void assign_constant_locations();
+   bool get_pull_locs(const fs_reg &src, unsigned *out_surf_index,
+                      unsigned *out_pull_index);
    void lower_constant_loads();
    void invalidate_live_intervals();
    void calculate_live_intervals();