Pages that we want to track for NOTDIRTY are RAM.  We do not
really need to go through the I/O path to handle them.
Acked-by: NDavid Hildenbrand <david@redhat.com>
Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>