radv: use nir_shrink_vec_array_vars()

radv: use nir_shrink_vec_array_vars()

Totals from affected shaders:
SGPRS: 1096 -> 1096 (0.00 %)
VGPRS: 1192 -> 1056 (-11.41 %)
Spilled SGPRs: 0 -> 0 (0.00 %)
Spilled VGPRs: 0 -> 0 (0.00 %)
Private memory VGPRs: 0 -> 0 (0.00 %)
Scratch size: 0 -> 0 (0.00 %) dwords per thread
Code Size: 100940 -> 94384 (-6.49 %) bytes
LDS: 0 -> 0 (0.00 %) blocks
Max Waves: 100 -> 112 (12.00 %)
Wait states: 0 -> 0 (0.00 %)

All affected shaders are from Batman Arkham City.

Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>