[PATCH] SIS900 must select MII

This patch fixes the following compile error caused by bk-netdev:

<--  snip  -->

...
  LD      .tmp_vmlinux1
drivers/built-in.o(.text+0x98528): In function `sis900_get_settings':
: undefined reference to `mii_ethtool_gset'
drivers/built-in.o(.text+0x98538): In function `sis900_set_settings':
: undefined reference to `mii_ethtool_sset'
drivers/built-in.o(.text+0x98517): In function `sis900_get_link':
: undefined reference to `mii_link_ok'
drivers/built-in.o(.text+0x98547): In function `sis900_nway_reset':
: undefined reference to `mii_nway_restart'
make: *** [.tmp_vmlinux1] Error 1

<--  snip  -->

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Daniele Venzano <venza@brownhat.org>