net: atheros: atl2: don't return zero on failure path in atl2_probe()

If dma mask checks fail in atl2_probe(), it breaks off initialization,
deallocates all resources, but returns zero.

The patch adds proper error code return value and
make error code setup unified.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>