When a request is made to register a filter on a fifo that doesn't apply to the fifo (i.e., not EVFILT_READ or EVFILT_WRITE), reject it as EINVAL, not by returning 1 (EPERM).
When a request is made to register a filter on a fifo that doesn't
apply to the fifo (i.e., not EVFILT_READ or EVFILT_WRITE), reject
it as EINVAL, not by returning 1 (EPERM).

MFC after:	3 days

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