[AMDGPU] GFX12 VMEM loads can write VGPR results out of order (llvm#105549)

Fix SIInsertWaitcnts to account for this by adding extra waits to avoid
WAW dependencies.

(cherry picked from commit 5506831)

Author: jayfoad

llvm/test/CodeGen/AMDGPU/load-global-i32.ll

@@ -3154,8 +3154,10 @@ define amdgpu_kernel void @global_sextload_v32i32_to_v32i64(ptr addrspace(1) %ou
 ; SI-NOHSA-NEXT:    buffer_store_dwordx4 v[36:39], off, s[0:3], 0 offset:240
 ; SI-NOHSA-NEXT:    buffer_store_dwordx4 v[32:35], off, s[0:3], 0 offset:192
 ; SI-NOHSA-NEXT:    buffer_load_dword v8, off, s[12:15], 0 ; 4-byte Folded Reload
+; SI-NOHSA-NEXT:    s_waitcnt vmcnt(0)
 ; SI-NOHSA-NEXT:    buffer_load_dword v9, off, s[12:15], 0 offset:4 ; 4-byte Folded Reload
 ; SI-NOHSA-NEXT:    buffer_load_dword v10, off, s[12:15], 0 offset:8 ; 4-byte Folded Reload
+; SI-NOHSA-NEXT:    s_waitcnt vmcnt(0)
 ; SI-NOHSA-NEXT:    buffer_load_dword v11, off, s[12:15], 0 offset:12 ; 4-byte Folded Reload
 ; SI-NOHSA-NEXT:    s_waitcnt vmcnt(0)
 ; SI-NOHSA-NEXT:    buffer_store_dwordx4 v[8:11], off, s[0:3], 0 offset:208