The SMI bus ID for RTL8231 currently defaults to 0, and can be
overridden from the devicetree. However, there is no value check on the
DT-provided value, aside from masking which would only cause value
wrap-around.
Change the driver to always require the "indirect-access-bus-id"
property, as there is no real reason to use 0 as default, and perform a
sanity check on the value when probing. This allows the other parts of
the driver to be simplified a bit.
Signed-off-by: Sander Vanheule <sander@svanheule.net>
Tested-by: Stijn Tintel <stijn@linux-ipv6.be>