isdn/gigaset: correct bas_gigaset rx buffer handling

isdn/gigaset: correct bas_gigaset rx buffer handling

commit f3d531b99fb30945b4a64d6e2e86e1e62605aca5 upstream.

In transparent data reception, avoid a NULL pointer dereference
in case an skbuff cannot be allocated, remove an inappropriate
call to the HDLC flush routine, and correct the accounting of
received bytes for continued buffers.

Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andi Kleen <ak@linux.intel.com>