USB: serial: io_ti: remove some remaining printk() calls

Use dev_err() like the rest of that function does, and the rest of the
driver does, to properly show what device and driver caused the problem.

Cc: Johan Hovold <jhovold@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>