r8152: modify rtl8152_set_speed function

First, for AUTONEG_DISABLE, we only need to modify MII_BMCR.

Second, add advertising parameter for rtl8152_set_speed(). Add
RTL_ADVERTISED_xxx for advertising parameter of rtl8152_set_speed().
Then, the advertising settings from ethtool could be saved.

Signed-off-by: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>