pwm: imx: add Kconfig support

add Kconfig support for this driver.

Signed-off-by: Heiko Schocher <hs@denx.de>
Acked-by: Martyn Welch <martyn.welch@collabora.co.uk>
diff --git a/configs/mx53ppd_defconfig b/configs/mx53ppd_defconfig
index a88af15..cad798a 100644
--- a/configs/mx53ppd_defconfig
+++ b/configs/mx53ppd_defconfig
@@ -43,6 +43,7 @@
 CONFIG_MII=y
 CONFIG_PINCTRL=y
 CONFIG_PINCTRL_IMX5=y
+CONFIG_PWM_IMX=y
 CONFIG_RTC_S35392A=y
 CONFIG_USB=y
 CONFIG_USB_EHCI_MX5=y