target-ppc: Clean Up mullw

Eliminate the unecessary ext32s TCG operation and make the multiplication
operation explicitly 32 bit.

Signed-off-by: Tom Musta <tommusta@gmail.com>
Suggested-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Alexander Graf <agraf@suse.de>

target-ppc/translate.c

@@ -1138,9 +1138,8 @@ static void gen_mullw(DisasContext *ctx)
     tcg_temp_free(t0);
     tcg_temp_free(t1);
 #else
-    tcg_gen_mul_tl(cpu_gpr[rD(ctx->opcode)], cpu_gpr[rA(ctx->opcode)],
-                   cpu_gpr[rB(ctx->opcode)]);
-    tcg_gen_ext32s_tl(cpu_gpr[rD(ctx->opcode)], cpu_gpr[rD(ctx->opcode)]);
+    tcg_gen_mul_i32(cpu_gpr[rD(ctx->opcode)], cpu_gpr[rA(ctx->opcode)],
+                    cpu_gpr[rB(ctx->opcode)]);
 #endif
     if (unlikely(Rc(ctx->opcode) != 0))
         gen_set_Rc0(ctx, cpu_gpr[rD(ctx->opcode)]);