device: add child traversal helper function
Add a function, dev_bus_each_child(), which walks through all the
children for a given bus of a device. This helper allows one to
walk through all the children of a given device's bus.
BUG=b:
111808427,b:
111743717
TEST=built
Change-Id: Iedceb0d19c05b7abd5a48f8dc30f85461bef5ec6
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/27636
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Justin TerAvest <teravest@chromium.org>