Revert "ima: limit file hash setting by user to fix and log modes"

Userspace applications have been modified to write security xattrs,
but they are not context aware.  In the case of security.ima, the
security xattr can be either a file hash or a file signature.
Permitting writing one, but not the other requires the application to
be context aware.

In addition, userspace applications might write files to a staging
area, which might not be in policy, and then change some file metadata
(eg. owner) making it in policy.  As a result, these files are not
labeled properly.

This reverts commit c68ed80c, which
prevents writing file hashes as security.ima xattrs.

Requested-by: Patrick Ohly <patrick.ohly@intel.com>
Cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>