net: macb: Add default usrio config to default gem config

There is no usrio config defined for default gem config leading to
a kernel panic devices that don't define a data. This issue can be
reprdouced with microchip polar fire soc where compatible string
is defined as "cdns,macb".

Fixes: edac6386

 ("add userio bits as platform configuration")

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>