ipwireless: Do not return value from sending funcs

ipwireless: Do not return value from sending funcs

Do not return value from do_send_fragment and do_send_packet, it's not used.
The packet size checks are not useful too:

* zero length packet will never be sent, caller always passes packet_header
  size which is either 1 or 3
* MTU check is done in caller, no need to repeat

Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>