security: pfe: Remove __exit annotation to fix section mismatch

pfk_ext4_deinit() is called from init code and we throw away
__exit marked code when modules are built-in. Remove the __exit
markings here so that we can always call this function even from
__init code. Similarly for pfk_ecryptfs_deinit().

Change-Id: I80a3304d84cdf18772879efe6c4a955d873b89c4
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>