Smc network IPs can be wired up in different funny ways. For example the
lubbock pxa25x development platform wires all address lines shifted by
2, ie. bus A2 is smc91c96 A0, bus A3 is smc91c96 A1 etc ...

In order to cope with the different possible combination, add a shift
parameter for addresses.

By default, the old behaviour using the 32 bit accesses is kept.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>