gigaset: remove UNDOCREQ config option

Drop the kernel config option GIGASET_UNDOCREQ, permanently
activating the code it controlled, as there have been no reports
of problems caused by its activation but many problems caused by
it being disabled.
Also fix a few bad comments while we're at it.

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