pwm, imx6: add support for pwm modul on imx6

add basic support for the pwm modul found on imx6.
Pieces of this code are based on linux code from drivers/pwm/pwm-imx.c
Commit "cd3de83f1476 Linux 3.16-rc4"

Signed-off-by: Heiko Schocher <hs@denx.de>
Acked-by: Stefano Babic <sbabic@denx.de>
Cc: Wolfgang Denk <wd@denx.de>
diff --git a/README b/README
index 4ac7399..a35b92c 100644
--- a/README
+++ b/README
@@ -1377,6 +1377,10 @@
 			CONFIG_SH_ETHER_CACHE_WRITEBACK
 			If this option is set, the driver enables cache flush.
 
+- PWM Support:
+		CONFIG_PWM_IMX
+		Support for PWM modul on the imx6.
+
 - TPM Support:
 		CONFIG_TPM
 		Support TPM devices.