evm: fix build problems

- Make the previously missing security_old_inode_init_security() stub
  function definition static inline.

- The stub security_inode_init_security() function previously returned
  -EOPNOTSUPP and relied on the callers to change it to 0.  The stub
  security/security_old_inode_init_security() functions now return 0.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>