AMDGPU: Use PseudoInstr instead of Pseudo Mnemonic for SIMCInstr, NFC (#87420)

Pseudo Mnemonic could be of other uses.

Author: changpeng

llvm/lib/Target/AMDGPU/DSInstructions.td

@@ -1192,7 +1192,7 @@ def : GCNPat <
 class Base_DS_Real_gfx6_gfx7_gfx10_gfx11_gfx12<bits<8> op, DS_Pseudo ps, int ef,
                                                string opName = ps.Mnemonic,
                                                bit hasGDS = true>
-    : DS_Real<ps, opName>, SIMCInstr <ps.Mnemonic, ef> {
+    : DS_Real<ps, opName>, SIMCInstr <ps.PseudoInstr, ef> {
 
   let Inst{7-0}   = !if(ps.has_offset0, offset0, 0);
   let Inst{15-8}  = !if(ps.has_offset1, offset1, 0);
@@ -1557,7 +1557,7 @@ defm DS_MAX_SRC2_F64        : DS_Real_gfx6_gfx7_gfx10<0x0d3>;
 
 class DS_Real_vi <bits<8> op, DS_Pseudo ps> :
   DS_Real <ps>,
-  SIMCInstr <ps.Mnemonic, SIEncodingFamily.VI> {
+  SIMCInstr <ps.PseudoInstr, SIEncodingFamily.VI> {
   let AssemblerPredicate = isGFX8GFX9;
   let DecoderNamespace = "GFX8";