The API of cpu_physical_memory_write_rom() is odd, because it
takes an AddressSpace, unlike all the other cpu_physical_memory_*
access functions. Rename it to address_space_write_rom(), and
bring its API into line with address_space_write().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Message-id: 20181122133507.30950-3-peter.maydell@linaro.org