migration: Fix operator type

Clang spotted an & that should have been an &&; fix it.

Reported by: David Binderman / https://gitlab.com/dcb
Fixes: 65dacaa0 ("migration: introduce save_normal_page()")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/963


Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20220406102515.96320-1-dgilbert@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>