evm: building without EVM enabled fixes

- Missing 'inline' on evm_inode_setattr() definition.
Introduced by commit 817b54aa45db ("evm: add evm_inode_setattr to prevent
updating an invalid security.evm").

- Missing security_old_inode_init_security() stub function definition.
Caused by commit 9d8f13ba3f48 ("security: new security_inode_init_security
API adds function callback").

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>