dtoc: extend dtoc to use struct driver_info when linking nodes

In the current implementation, when dtoc parses a dtb to generate a struct
platdata it converts the information related to linked nodes as pointers
to struct platdata of destination nodes. By doing this, it makes
difficult to get pointer to udevices created based on these
information.

This patch extends dtoc to use struct driver_info when populating
information about linked nodes, which makes it easier to later get
the devices created. In this context, reimplement functions like
clk_get_by_index_platdata() which made use of the previous approach.

Signed-off-by: Walter Lozano <walter.lozano@collabora.com>
Reviewed-by: Simon Glass <sjg@chromium.org>