evm: call evm_inode_init_security from security_inode_init_security

Changelog v7:
- moved the initialization call to security_inode_init_security,
  renaming evm_inode_post_init_security to evm_inode_init_security
- increase size of xattr array for EVM xattr

Signed-off-by: Mimi Zohar <zohar@us.ibm.com>