of: move documentation of of_parse_phandle_with_args

Commit bd69f73f "of: Create function for counting number of phandles in
a property" renamed of_parse_phandle_with_args(), and created a wrapper
function that implemented the original name. However, the documentation
of the original function was not moved, leaving it apparently documenting
the newly renamed function.

Move the documentation so that it is adjacent to the function it
documents.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Grant Likely <grant.likely@linaro.org>