qeth: fix build of s390 allmodconfig

commit 949efd1c "qeth: bridgeport support - basic control" broke
s390 allmodconfig. This patch fixes this by eliminating one of the
cross-module calls, and by making two other calls via function
pointers in the qeth_discipline structure.

Signed-off-by: Eugene Crosser <Eugene.Crosser@ru.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Reported-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>