ot1200: remove superfluous "string" tag

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Reviewed-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/board/bachmann/ot1200/Kconfig b/board/bachmann/ot1200/Kconfig
index 55a825d..6cf2573 100644
--- a/board/bachmann/ot1200/Kconfig
+++ b/board/bachmann/ot1200/Kconfig
@@ -1,23 +1,18 @@
 if TARGET_OT1200
 
 config SYS_CPU
-	string
 	default "armv7"
 
 config SYS_BOARD
-	string
 	default "ot1200"
 
 config SYS_VENDOR
-	string
 	default "bachmann"
 
 config SYS_SOC
-	string
 	default "mx6"
 
 config SYS_CONFIG_NAME
-	string
 	default "ot1200"
 
 endif