Fix two problems in the ch(4) driver.
Fix two problems in the ch(4) driver.

- Mike Smith discovered a panic in the changer probe code if the probe
  command (mode sense) fails.  So we need to release the CCB used in the
  probe before we unlock the peripheral.  (i.e. the same fix mjacob put in
  the CD and DA drivers)

- A newline was missing in a warning message.  (PR kern/17512)

PR:		kern/17512
Submitted by:	Louis Mamakos <louie@uu.net> (newline fix)

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