radv: Use structured intrinsics instead of indexing workaround for GFX9.

radv: Use structured intrinsics instead of indexing workaround for GFX9.

These force the index to be used in the instruction so we don't need the
workaround.

Totals:
SGPRS: 1321642 -> 1321802 (0.01 %)
VGPRS: 943664 -> 943788 (0.01 %)
Spilled SGPRs: 28468 -> 28480 (0.04 %)
Spilled VGPRs: 88 -> 89 (1.14 %)
Private memory VGPRs: 0 -> 0 (0.00 %)
Scratch size: 80 -> 80 (0.00 %) dwords per thread
Code Size: 52415292 -> 52338932 (-0.15 %) bytes
LDS: 400 -> 400 (0.00 %) blocks
Max Waves: 233903 -> 233803 (-0.04 %)
Wait states: 0 -> 0 (0.00 %)

Totals from affected shaders:
SGPRS: 238344 -> 238504 (0.07 %)
VGPRS: 232732 -> 232856 (0.05 %)
Spilled SGPRs: 13125 -> 13137 (0.09 %)
Spilled VGPRs: 88 -> 89 (1.14 %)
Private memory VGPRs: 0 -> 0 (0.00 %)
Scratch size: 80 -> 80 (0.00 %) dwords per thread
Code Size: 15752712 -> 15676352 (-0.48 %) bytes
LDS: 139 -> 139 (0.00 %) blocks
Max Waves: 31680 -> 31580 (-0.32 %)
Wait states: 0 -> 0 (0.00 %)

Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>