usbnet: smsc95xx: rename FEATURE_AUTOSUSPEND

The name of FEATURE_AUTOSUSPEND is very misleading and the actual
meaning is remote wakeup, but a device incapable of remote wakeup
still can support USB autosuspend under some situations, so rename
it to avoid misunderstanding.

Cc: Steve Glendinning <steve.glendinning@shawell.net>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>