pwm: add pca9685 driver

Add pwm driver for the NXP pca9685 16 channel pwm-led controller.

The driver is really barebones at this stage. E.g. the OE' pin and
therefore the corresponding registers are not supported.
The driver was tested on a HW where this pin is tied to GND.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
[thierry.reding@gmail.com: style and whitespace cleanups]
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 115b644..d3fe320 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -97,6 +97,15 @@
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-mxs.
 
+config PWM_PCA9685
+	tristate "NXP PCA9685 PWM driver"
+	depends on OF && REGMAP_I2C
+	help
+	  Generic PWM framework driver for NXP PCA9685 LED controller.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-pca9685.
+
 config PWM_PUV3
 	tristate "PKUnity NetBook-0916 PWM support"
 	depends on ARCH_PUV3