Clarify c1, c2, c3 in negative path delay log message.

Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
Change level of negative path delay messages to debug.

Negative path delay measurements are expected with E2E, the user doesn't
need to know when that happens.

Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
Print current frequency when PI servo is in unlocked state.

Store the current frequency and return it when the servo is in unlocked
state instead of zero. This fixes values printed in log messages.

Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
phc2sys: Mention that PPS output needs to be enabled without -s.

Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>