aco: allow p_start_linear_vgpr to use multiple operands

Merging the p_create_vector into the p_start_linear_vgpr is useful since
we stopped attempting to place the p_start_linear_vgpr definition in the
same registers as the operand.

fossil-db (navi31):
Totals from 927 (1.17% of 79242) affected shaders:
MaxWaves: 26412 -> 26442 (+0.11%)
Instrs: 938328 -> 938181 (-0.02%); split: -0.14%, +0.13%
CodeSize: 4891448 -> 4890820 (-0.01%); split: -0.11%, +0.10%
VGPRs: 47016 -> 47004 (-0.03%); split: -0.13%, +0.10%
SpillSGPRs: 222 -> 226 (+1.80%)
Latency: 5076065 -> 5075191 (-0.02%); split: -0.12%, +0.10%
InvThroughput: 712316 -> 712421 (+0.01%); split: -0.09%, +0.10%
SClause: 27992 -> 27972 (-0.07%); split: -0.09%, +0.02%
Copies: 38042 -> 38104 (+0.16%); split: -1.95%, +2.12%
PreVGPRs: 39448 -> 39369 (-0.20%)
VALU: 570157 -> 570224 (+0.01%); split: -0.13%, +0.14%
SALU: 51672 -> 51678 (+0.01%); split: -0.01%, +0.02%

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27697>

src/amd/compiler/aco_optimizer.cpp

@@ -580,6 +580,7 @@ pseudo_propagate_temp(opt_ctx& ctx, aco_ptr<Instruction>& instr, Temp temp, unsi
    case aco_opcode::p_linear_phi:
    case aco_opcode::p_parallelcopy:
    case aco_opcode::p_create_vector:
+   case aco_opcode::p_start_linear_vgpr:
       if (temp.bytes() != instr->operands[index].bytes())
          return false;
       break;