leds: pca955x: add GPIO support

The PCA955x family of chips are I2C LED blinkers whose pins not used
to control LEDs can be used as general purpose I/Os (GPIOs).

The following adds such a support by defining different operation
modes for the pins (See bindings documentation for more details). The
pca955x driver is then extended with a gpio_chip when some of pins are
operating as GPIOs. The default operating mode is to behave as a LED.

The GPIO support is conditioned by CONFIG_LEDS_PCA955X_GPIO.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>

include/dt-bindings/leds/leds-pca955x.h

@@ -0,0 +1,16 @@
+/*
+ * This header provides constants for pca955x LED bindings.
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2.  This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#ifndef _DT_BINDINGS_LEDS_PCA955X_H
+#define _DT_BINDINGS_LEDS_PCA955X_H
+
+#define PCA955X_TYPE_NONE         0
+#define PCA955X_TYPE_LED          1
+#define PCA955X_TYPE_GPIO         2
+
+#endif /* _DT_BINDINGS_LEDS_PCA955X_H */