target/mips: Add a placeholder for R5900 LQ

Add a placeholder for LQ instruction.
Reviewed-by: NAleksandar Markovic <amarkovic@wavecomp.com>
Signed-off-by: NFredrik Noring <noring@nocrew.org>
Signed-off-by: NAleksandar Markovic <amarkovic@wavecomp.com>

target/mips/translate.c

@@ -24420,6 +24420,11 @@ static void decode_opc_special3_legacy(CPUMIPSState *env, DisasContext *ctx)
     }
 }
 
+static void decode_tx79_lq(CPUMIPSState *env, DisasContext *ctx)
+{
+    generate_exception_end(ctx, EXCP_RI);    /* TODO: TX79_LQ */
+}
+
 static void gen_tx79_sq(DisasContext *ctx, int base, int rt, int offset)
 {
     generate_exception_end(ctx, EXCP_RI);    /* TODO: TX79_SQ */
@@ -26425,8 +26430,12 @@ static void decode_opc(CPUMIPSState *env, DisasContext *ctx)
         }
         break;
     case OPC_MSA: /* OPC_MDMX */
-        /* MDMX: Not implemented. */
-        gen_msa(env, ctx);
+        if (ctx->insn_flags & INSN_R5900) {
+            decode_tx79_lq(env, ctx);    /* TX79_LQ */
+        } else {
+            /* MDMX: Not implemented. */
+            gen_msa(env, ctx);
+        }
         break;
     case OPC_PCREL:
         check_insn(ctx, ISA_MIPS32R6);