ctcm: avoid crash in ctcm_remove_device

Channels are already removed when setting a ctcm-device offline.
Thus ctcm_remove_device must not refer to channel information.
Solution: delete channel information from the trace call in
ctcm_remove_device.

Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>