pwm: ti: am33xx: add enhanced pwm driver

Enhanced high resolution PWM module (EHRPWM) hardware can be used to
generate PWM output over 2 channels. This commit adds PWM driver support
for EHRPWM device present on AM33XX SOC.

The code is based on the drivers/pwm/pwm-tiehrpwm.c driver of the Linux
kernel version 5.9-rc7.
For DT binding details see:
- Documentation/devicetree/bindings/pwm/pwm-tiehrpwm.txt

Signed-off-by: Dario Binacchi <dariobin@libero.it>
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index b3bd5c6..ccf81ab 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -75,3 +75,10 @@
 	help
 	  This PWM is found on H3, A64 and other Allwinner SoCs. It supports a
 	  programmable period and duty cycle. A 16-bit counter is used.
+
+config PWM_TI_EHRPWM
+	bool "Enable support for EHRPWM PWM"
+	depends on DM_PWM && ARCH_OMAP2PLUS
+	default y
+	help
+	  PWM driver support for the EHRPWM controller found on TI SOCs.