linux-phytec-ti

doc: Fix acronym "FEKEK" in ecryptfs

"FEFEK" was incorrectly used as acronym for "File Encryption Key
Encryption Key". This replaces all occurences with "FEKEK".

Signed-off-by: Felix Eckhofer <felix@eckhofer.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>