hso: fix deadlock when receiving bursts of data

When the module sends bursts of data, sometimes a deadlock happens in
the hso driver when the tty buffer doesn't get the chance to be flushed
quickly enough.

Remove the endless while loop in function put_rxbuf_data() which is
called by the urb completion handler.
If there isn't enough room in the tty buffer, discards all the data
received in the URB.

Cc: David Miller <davem@davemloft.net>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: Dan Williams <dcbw@redhat.com>
Cc: Jan Dumon <j.dumon@option.com>
Signed-off-by: Olivier Sobrie <olivier@sobrie.be>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>