Add CFG_RTC_DS1337_NOOSC to turn off OSC output

The default settings for RTC DS1337 keeps the OSC
output, 32,768 Hz, on. This add CFG_RTC_DS1337_NOOSC to
turn it off.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
diff --git a/README b/README
index a9663a3..b3423e3 100644
--- a/README
+++ b/README
@@ -689,6 +689,7 @@
 		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
 		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
 		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
+		CFG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
 
 		Note that if the RTC uses I2C, then the I2C interface
 		must also be configured. See I2C Support, below.