pwm: Add driver for Amlogic Meson PWM controller

This adds the driver for the PWM controller found in the Amlogic SoCs.

This PWM is only a set of Gates, Dividers and Counters:
PWM output is achieved by calculating a clock that permits calculating
two periods (low and high). The counter then has to be set to switch after
N cycles for the first half period.
The hardware has no "polarity" setting. This driver reverses the period
cycles (the low length is inverted with the high length) for
PWM_POLARITY_INVERSED.

Disabling the PWM stops the output immediately (without waiting for the
current period to complete first).

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 0f4e84b..f21ae7d 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -12,6 +12,7 @@
 
 obj-$(CONFIG_PWM_EXYNOS)	+= exynos_pwm.o
 obj-$(CONFIG_PWM_IMX)		+= pwm-imx.o pwm-imx-util.o
+obj-$(CONFIG_PWM_MESON)		+= pwm-meson.o
 obj-$(CONFIG_PWM_MTK)		+= pwm-mtk.o
 obj-$(CONFIG_PWM_ROCKCHIP)	+= rk_pwm.o
 obj-$(CONFIG_PWM_SANDBOX)	+= sandbox_pwm.o