common: fdt_support: add support for setting usable memory

common: fdt_support: add support for setting usable memory

Add support for setting linux,usable-memory property in the memory
node of device tree for the kernel [1].

This property holds a base address and size, describing a
limited region in which memory may be considered available for use by
the kernel. Memory outside of this range is not available for use.

[1] https://www.kernel.org/doc/Documentation/devicetree/bindings/chosen.txt

Signed-off-by: Igor Opaniuk <[email protected]>
Signed-off-by: Sanchayan Maity <[email protected]>
Signed-off-by: Stefan Agner <[email protected]>
Reviewed-by: Oleksandr Suvorov <[email protected]>