target/s390x: Hoist some computation in access_memmove

Ensure that the total length is in a local variable
across the byte loop.  Compute size1 difference once.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Message-Id: <20230109201856.3916639-8-richard.henderson@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>
1 file changed