ima: generic IMA action flag handling

Make the IMA action flag handling generic in order to support
additional new actions, without requiring changes to the base
implementation.  New actions, like audit logging, will only
need to modify the define statements.

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>