When CONFIG_ARM_APPENDED_DTB is selected, if the bootloader provides
an ATAG_MEM it replaces the memory size and the memory address in the
memory node of the device tree. In the case of a system which can
handle more than 4GB, the memory node cell size is 4: each data
(memory size and memory address) are 64 bits and then use 2 cells.

The current code in atags_to_fdt.c made the assumption of a cell size
of 2 (one cell for the memory size and one cell for the memory
address), this leads to an improper write of the data and ends with a
boot hang.

This patch writes the memory size and the memory address on the memory
node in the device tree depending of the size of the memory node (32
bits or 64 bits).

It has been tested in the 2 cases:
- with a dtb using skeleton.dtsi
- and with a dtb using skeleton64.dtsi

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>