libfdt: Add functions to get/add/delete memory reservemap entries

[Jon Loeliger]

So, like, the other day David Gibson mumbled:
> This patch adds functions to libfdt for accessing the memory
> reservation map section of a device tree blob.  fdt_num_mem_rsv()
> retreives the number of reservation entries in a dtb, and
> fdt_get_mem_rsv() retreives a specific reservation entry.
> fdt_add_mem_rsv() adds a new entry, and fdt_del_mem_rsv() removes a
> specific numbered entry.
> 
> Testcases for these new functions are also included.
> 
> Signed-off-by: David Gibson <david at gibson.dropbear.id.au>

Applied.

Thanks,
jdl