arm: mvebu: fix length of SATA registers area in .dtsi

The length of the registers area for the Marvell 370/XP SATA
controller was incorrect in the .dtsi: 0x2400 while it should have
been 0x5000. Until now, this problem wasn't noticed because there was
a large static mapping for all I/Os set up by ->map_io(). But since
we're going to get rid of this static mapping, we need to ensure that
the register areas are properly sized.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>