sunxi: spl: Fix DRAM info printing

The switch to simple_printf was causing the SPL dram info to show as:

DRAM: u MiB

This fixes this by switching from %lu to %d for printing the DRAM size.

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