of: Introduce of_for_each_phandle() helper macro

With this macro any user can easily iterate over a list of
phandles. The patch also converts __of_parse_phandle_with_args()
to make use of the macro.

The of_count_phandle_with_args() function is not converted,
because the macro hides the return value of of_phandle_iterator_init(),
which is needed in there.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Rob Herring <robh@kernel.org>
diff --git a/drivers/of/base.c b/drivers/of/base.c
index fcff2b6..ea5a13d 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -1543,13 +1543,8 @@
 	struct of_phandle_iterator it;
 	int rc, cur_index = 0;
 
-	rc = of_phandle_iterator_init(&it, np, list_name,
-				      cells_name, cell_count);
-	if (rc)
-		return rc;
-
 	/* Loop over the phandles until all the requested entry is found */
-	while ((rc = of_phandle_iterator_next(&it)) == 0) {
+	of_for_each_phandle(&it, rc, np, list_name, cells_name, cell_count) {
 		/*
 		 * All of the error cases bail out of the loop, so at
 		 * this point, the parsing is successful. If the requested