security: remove redundant assignment to return variable

In the case where rc is equal to EOPNOTSUPP it is being reassigned a
new value of zero that is never read. The following continue statement
loops back to the next iteration of the lsm_for_each_hook loop and
rc is being re-assigned a new value from the call to getselfattr.
The assignment is redundant and can be removed.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
[PM: subj tweak]
Signed-off-by: Paul Moore <paul@paul-moore.com>