of: Improve of_phandle_iterator_next() error message

Understanding why of_phandle_iterator_next() returns an error can
sometimes be hard to decipher based solely on the error message, a
typical error example is that #foo-cells = <X> and the phandle property
used has a smaller number of cells specified, e.g.:

#thermal-sensor-cells = <1>;
phandle = <&scmi_sensor>

instead of:

phandle <&scmi_sensor 0>;

Instead, make it clear what the expectations are towards debugging
incorrect Device Tree faster:

OF: /thermal-zones/scmi-thermal: #thermal-sensor-cells = 1, found 0 instead

Signed-off-by: Florian Fainelli <[e-mail]>
Signed-off-by: Rob Herring <[e-mail]>

drivers/of/base.c

···
 		 * property data length
 		 */
 		if (it->cur + count > it->list_end) {
-			pr_err("%pOF: arguments longer than property\n",
-			       it->parent);
+			pr_err("%pOF: %s = %d found %d\n",
+			       it->parent, it->cells_name,
+			       count, it->cell_count);
 			goto err;
 		}
 	}