[PATCH] introduce CONFIG_DEVICE_TREE_INCLUDES

[Rasmus Villemoes]

Please note that this is not a resubmission of fdt_add_pubkey, I merely
mentioned that in passing (and cc'ed Roman because of his interest in
that) as a previous attempt at solving the problem of getting the public
key info baked into U-Boot's .dtb, an approach that I've since learnt is
not without problems of its own. So please review this patch on its own
merits.

Rasmus