ima: measure and appraise the IMA policy itself

Call ima_hash_and_process_file() to measure and appraise the IMA policy.
This patch defines a new policy identifier named POLICY_CHECK.

Changelog v2:
- remove S_ISREG() test
- add union name "hooks" to fix sparse warning

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
7 files changed