target/s390x: Fix assertion failure in VFMIN/VFMAX with type 13

Type 13 is reserved, so using it should result in specification
exception. Due to an off-by-1 error the code triggers an assertion at a
later point in time instead.

Cc: qemu-stable@nongnu.org
Fixes: da48075 ("s390x/tcg: Implement VECTOR FP (MAXIMUM|MINIMUM)")
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-Id: <20230724082032.66864-8-iii@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
(cherry picked from commit ff537b0)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

target/s390x/tcg/translate_vx.c.inc

@@ -3047,7 +3047,7 @@ static DisasJumpType op_vfmax(DisasContext *s, DisasOps *o)
     const uint8_t m5 = get_field(s, m5);
     gen_helper_gvec_3_ptr *fn;
 
-    if (m6 == 5 || m6 == 6 || m6 == 7 || m6 > 13) {
+    if (m6 == 5 || m6 == 6 || m6 == 7 || m6 >= 13) {
         gen_program_exception(s, PGM_SPECIFICATION);
         return DISAS_NORETURN;
     }