net/sb1250: remove CONFIG_SIBYTE_STANDALONE

CONFIG_SIBYTE_STANDALONE is gone since v2.6.31-rc1 ("MIPS: Sibyte:
Remove standalone kernel support")
This is a missing piece.

Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>