of: Merge of_address_to_resource() and of_pci_address_to_resource() implementations

of_address_to_resource() and of_pci_address_to_resource() are almost the
same except the former takes an index and the latter takes a BAR number.
Now that __of_get_address() can take either one, refactor the functions
to use a common implementation.

Cc: Frank Rowand <frowand.list@gmail.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210527194547.1287934-5-robh@kernel.org