arm: mvebu: db-mv784mp-gp: Switch from IDE to SATA support

Enable the newly introduced SATA driver for the Marvell AXP with DMA
support instead of the PIO-only IDE driver. This increases the
transfer speed. And is also more in-line with the Armada 38x
ports, which also use a SATA driver (AHCI) and the "sata" U-Boot
commands.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Luka Perkov <luka.perkov@sartura.hr>