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

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: da4807527f3b ("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 ff537b0370ab5918052b8d8a798e803c47272406)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>