mount: losetup: remove obsolete encryption support

mount: losetup: remove obsolete encryption support

kernel cryptoloop is deprecated since ages and support for cryptoloop
in util-linux is incomplete/broken.
- no password hashing
- last 8 bit of key are always set to zero
- no binary keys possible (stops reading key at \n and \0)

In the past some Distros added the above features with patches. So
remove cryptoloop support from util-linux completely to make sure
people won't try using it.

Signed-off-by: Ludwig Nussel <ludwig.nussel@suse.de>
Signed-off-by: Karel Zak <kzak@redhat.com>