st/mesa: move the logic of all_varyings_in_vbos into st_update_array

The function was pretty slow. This brings a substantial decrease in draw
call overhead when min/max index bounds are not needed:

Before:  DrawElements (1 VBO) w/ no state change:          5.75 million
After:   DrawElements (1 VBO) w/ no state change:          7.03 million

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
3 files changed