cxgb3: commnonize LASI phy code

Add generic code to manage interrupt driven PHYs.
Do not reset the phy after link parameters update,
the new values might get lost.
Return early from link change notification
when the link parameters remain unchanged.

Signed-off-by: Divy Le Ray <divy@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>