Kbuild/doc: fix links to Documentation files

Fix links to files in Documentation/* in various Kconfig files

Signed-off-by: Dirk Hohndel <hohndel@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 4ec716d..1330061 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -513,7 +513,7 @@
 	default n
 	help
 	  Select this option if you want to build an zfcpdump enabled kernel.
-	  Refer to "Documentation/s390/zfcpdump.txt" for more details on this.
+	  Refer to <file:Documentation/s390/zfcpdump.txt> for more details on this.
 
 endmenu