dm: core: add ofnode_count_phandle_with_args()

This function is usefull to get phandle number contained
in a property list.
For example,  this allows to allocate the right amount
of memory to keep clock's reference contained into the
"clocks" property.

To implement it, either of_count_phandle_with_args() or
fdtdec_parse_phandle_with_args() are used respectively
for live tree and flat tree.
By passing index = -1, these 2 functions returns the
number of phandle contained into the property list.

Add also the dev_count_phandle_with_args() based on
ofnode_count_phandle_with_args()

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/core/of_access.c

@@ -665,6 +665,13 @@ int of_parse_phandle_with_args(const struct device_node *np,
 					    index, out_args);
 }
 
+int of_count_phandle_with_args(const struct device_node *np,
+			       const char *list_name, const char *cells_name)
+{
+	return __of_parse_phandle_with_args(np, list_name, cells_name, 0,
+					    -1, NULL);
+}
+
 static void of_alias_add(struct alias_prop *ap, struct device_node *np,
 			 int id, const char *stem, int stem_len)
 {