There are 2 reasons for doing this:

1) The main reason for doing this is to move it outside of
   board/sunxi/ahci.c, so that it can be used on boards which use
   a usb<->sata chip too;
2) While doing this I realized that doing it from board_init also meant
   doing it much earlier. Some printf get_timer(0) calls show that the
   time between board_init() and scsi_init() is more then 600 ms,
   so we can drop the mdelay(500)

While at it also drop the printf("SUNXI SCSI INIT\n") AHCI init is
noisy enough by itself.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>