common/cmd_fdt.c: fix wrong data displayed in fdt print

All data in dtb is big endian. Some ARM devices are little-endian.
In print_data(), it displays data with big-endian format. For ARM device,
data should be converted to little-endian first.

Signed-off-by: Haojian Zhuang <haojian.zhuang@marvell.com>
Cc: Gerald Van Baren <vanbaren@cideas.com>