rtc: ds1337: drop "SYS" from config variables

There is some inconsistency between uses of CONFIG_RTC_DS13xx and
CONFIG_SYS_RTC_DS13xx. Address this by dropping the "SYS" from
these variables.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/README b/README
index 075d919..a4a9c3b 100644
--- a/README
+++ b/README
@@ -1015,7 +1015,7 @@
 		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
 		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
 		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
-		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
+		CONFIG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
 		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
 					  RV3029 RTC.