Kconfig.debug: Grammar s/addition/additional/

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

lib/Kconfig.debug

@@ -576,8 +576,8 @@ config DEBUG_HIGHMEM
 	bool "Highmem debugging"
 	depends on DEBUG_KERNEL && HIGHMEM
 	help
-	  This options enables addition error checking for high memory systems.
-	  Disable for production systems.
+	  This option enables additional error checking for high memory
+	  systems.  Disable for production systems.
 
 config HAVE_DEBUG_STACKOVERFLOW
 	bool