fix a typo in the RTC_CLASS help text

This patch fixes a typo spotted by
Matt LaPlante <webmaster@cyberdogtech.com>.

This patch fixes kernel Bugzilla #6704.
Signed-off-by: NAdrian Bunk <bunk@stusta.de>

drivers/rtc/Kconfig

@@ -15,7 +15,7 @@ config RTC_CLASS
 	help
 	  Generic RTC class support. If you say yes here, you will
  	  be allowed to plug one or more RTCs to your system. You will
-	  probably want to enable one of more of the interfaces below.
+	  probably want to enable one or more of the interfaces below.
 
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-class.