doc: ReSTify keys-request-key.txt

Adjusts for ReST markup and moves under keys security devel index.

Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

security/keys/request_key.c

@@ -8,7 +8,7 @@
  * as published by the Free Software Foundation; either version
  * 2 of the License, or (at your option) any later version.
  *
- * See Documentation/security/keys-request-key.txt
+ * See Documentation/security/keys/request-key.rst
  */
 
 #include <linux/module.h>

security/keys/request_key_auth.c

@@ -8,7 +8,7 @@
  * as published by the Free Software Foundation; either version
  * 2 of the License, or (at your option) any later version.
  *
- * See Documentation/security/keys-request-key.txt
+ * See Documentation/security/keys/request-key.rst
  */
 
 #include <linux/module.h>