docs: Fix paths in security/keys

Several paths in the security/keys documentation were incorrect.

Signed-off-by: Josh Holland <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/security/keys/core.rst

···
      /sbin/request-key will be invoked in an attempt to obtain a key. The
      callout_info string will be passed as an argument to the program.
 
-     See also Documentation/security/keys-request-key.txt.
+     See also Documentation/security/keys/request-key.rst.
 
 
 The keyctl syscall functions are:
···
     If successful, the key will have been attached to the default keyring for
     implicitly obtained request-key keys, as set by KEYCTL_SET_REQKEY_KEYRING.
 
-    See also Documentation/security/keys-request-key.txt.
+    See also Documentation/security/keys/request-key.rst.
 
 
  *  To search for a key, passing auxiliary data to the upcaller, call::

Documentation/security/keys/request-key.rst

···
 ===================
 
 The key request service is part of the key retention service (refer to
-Documentation/security/keys.txt).  This document explains more fully how
+Documentation/security/core.rst).  This document explains more fully how
 the requesting algorithm works.
 
 The process starts by either the kernel requesting a service by calling

Documentation/security/keys/trusted-encrypted.rst

···
 are anticipated.  In particular the new format 'ecryptfs' has been defined in
 in order to use encrypted keys to mount an eCryptfs filesystem.  More details
 about the usage can be found in the file
-``Documentation/security/keys-ecryptfs.txt``.
+``Documentation/security/keys/ecryptfs.rst``.