Due to slight differences in behaviour accessing the registers for the
esp and le devices, create two separate SPARC32_DMA_DEVICE types and
update the sun4m machine to use.

Note that by using different device types we already know the size of
the register block and the value of is_ledma at init time, allowing us to
drop the SPARC32_DMA_DEVICE realize function and the is_ledma device
property.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Artyom Tarasenko <atar4qemu@gmail.com>
Acked-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>