[PATCH u-boot-dm] fdt_support: Add fdt_for_each_node_by_compatible() helper macro

[Marek Behún]

Hello Simon, Stefan,

this patch is for u-boot-dm, but will apply only after marvell/next is
merged.

Could we perhaps review it and let Stefan apply it on marvell/next?

BTW it passed CI on github.

Marek