target/ppc: mtmsrd is an illegal instruction on BookE

MSR is a 32-bit register in BookE and there is no mtmsrd instruction.

Cc: Christian Zigotzky <chzigotzky@xenosoft.de>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Message-Id: <20210706051321.609046-1-npiggin@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

target/ppc/translate.c

@@ -4940,6 +4940,11 @@ static void gen_mtcrf(DisasContext *ctx)
 #if defined(TARGET_PPC64)
 static void gen_mtmsrd(DisasContext *ctx)
 {
+    if (unlikely(!is_book3s_arch2x(ctx))) {
+        gen_invalid(ctx);
+        return;
+    }
+
     CHK_SV;
 
 #if !defined(CONFIG_USER_ONLY)