isdn/gigaset: try USB reset for bas_gigaset error recovery

In error_reset(), if sending HD_RESET_INTERRUPT_PIPE to the device
fails, try performing an USB reset.
Also correct an error in the leading comment.

Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>