telephony: phonedev panics if unregistering device not registered [Bug 9266]

Remove panic from phonedev.  See

	http://bugzilla.kernel.org/show_bug.cgi?id=9266

for details (phonedev panics if unregistering device not registered).

Signed-off-by: Matti Linnanvuori <mattilinnanvuori@yahoo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>