aco: simplify gathering of MIMG address components
This patch has a slight effect on pipelinedb: Totals from affected shaders: SGPRS: 23616 -> 21504 (-8.94 %) VGPRS: 15088 -> 14444 (-4.27 %) 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: 662660 -> 664600 (0.29 %) bytes LDS: 49 -> 49 (0.00 %) blocks Max Waves: 3079 -> 3204 (4.06 %) Reviewed-by:Rhys Perry <pendingchaos02@gmail.com> Tested-by: Marge Bot <mesa/mesa!3602> Part-of: <mesa/mesa!3602>