sparc32_dma: make esp device child of espdma device

sparc32_dma: make esp device child of espdma device

This makes it possible to reference the esp device from the espdma device as
required, and by wiring up the device ourselves in sun4m.c we can drop use
of the esp_init() function.

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>