FROMLIST: of: Export of_phandle_iterator_args() to modules

Kernel modules may want to use of_phandle_iterator_args(),
so export it.

Change-Id: Ic42b0917834669dd4dc6930081581d66381c7d5a
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>
Acked-by: Rob Herring <robh@kernel.org>
Bug: 140290589
Link: https://patchwork.kernel.org/patch/10948415/