pwm: Add SPEAr PWM chip driver support

Add support for PWM chips present on SPEAr platforms. These PWM
chips support 4 channel output with programmable duty cycle and
frequency.

More details on these PWM chips can be obtained from relevant
chapter of reference manual, present at following[1] location.

1. http://www.st.com/internet/mcu/product/251211.jsp

Cc: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Shiraz Hashim <shiraz.hashim@st.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Vipin Kumar <vipin.kumar@st.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index ed81720..6e556c7 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -112,6 +112,17 @@
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-samsung.
 
+config PWM_SPEAR
+	tristate "STMicroelectronics SPEAr PWM support"
+	depends on PLAT_SPEAR
+	depends on OF
+	help
+	  Generic PWM framework driver for the PWM controller on ST
+	  SPEAr SoCs.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-spear.
+
 config PWM_TEGRA
 	tristate "NVIDIA Tegra PWM support"
 	depends on ARCH_TEGRA