encrypted-keys: move ecryptfs documentation to proper location

Move keys-ecryptfs.txt to Documentation/security.

Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

diff --git a/Documentation/keys-ecryptfs.txt b/Documentation/security/keys-ecryptfs.txt
similarity index 100%
rename from Documentation/keys-ecryptfs.txt
rename to Documentation/security/keys-ecryptfs.txt