Port Key was determined as 16 bits according to the link speed,
duplex and user key (which is yet not supported).  In the old
speed field, 5 bits are for speed [1|10|100|1000|10000]Mbps as
below:
--------------------------------------------------------------
Port key :| User key        | Speed         |       Duplex|
--------------------------------------------------------------
    16                  6               1               0
This patch keeps the old layout, but changes AD_LINK_SPEED_BITMASK
from bit type to an enum type.  In this way, the speed field can
expand speed type from 5 to 32.

CC: Jay Vosburgh <j.vosburgh@gmail.com>
CC: Veaceslav Falico <vfalico@gmail.com>
CC: Andy Gospodarek <andy@greyhouse.net>
CC: David S. Miller <davem@davemloft.net>
Signed-off-by: Jianhua Xie <jianhua.xie@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>