device: property: add helpers to count items in string arrays

Instead of doing the following:

    count = device_property_read_string_array(dev, propname, NULL, 0);

Let's provide inline helpers with hardcoded arguments for counting
strings in property arrays.
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

include/linux/property.h

@@ -170,6 +170,12 @@ static inline int device_property_count_u64(struct device *dev, const char *prop
 	return device_property_read_u64_array(dev, propname, NULL, 0);
 }
 
+static inline int device_property_string_array_count(struct device *dev,
+						     const char *propname)
+{
+	return device_property_read_string_array(dev, propname, NULL, 0);
+}
+
 static inline bool fwnode_property_read_bool(const struct fwnode_handle *fwnode,
 					     const char *propname)
 {
@@ -224,6 +230,13 @@ static inline int fwnode_property_count_u64(const struct fwnode_handle *fwnode,
 	return fwnode_property_read_u64_array(fwnode, propname, NULL, 0);
 }
 
+static inline int
+fwnode_property_string_array_count(const struct fwnode_handle *fwnode,
+				   const char *propname)
+{
+	return fwnode_property_read_string_array(fwnode, propname, NULL, 0);
+}
+
 struct software_node;
 
 /**