WB2CSR: Use CSR address_width for the wishbone bus

WB2CSR: Use CSR address_width for the wishbone bus

Currently, we create a wishbone interface with the default address
width (30 bits) for the bridge. Instead, create an interface that
has the same number of address bits as the CSR bus.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>