net: sfp: control TX_DISABLE and phy only from main state machine

We initialise TX_DISABLE when the sfp cage is probed, and then
maintain its state in the main state machine.  However, the module
state machine:
- negates it when detecting a newly inserted module when it's already
  guaranteed to be negated.
- negates it when the module is removed, but the main state machine
  will do this anyway.

Make TX_DISABLE entirely controlled by the main state machine.

The main state machine also probes the module for a PHY, and removes
the PHY when the the module is removed.  Hence, removing the PHY in
sfp_sm_module_remove() is also redundant, and is a left-over from
when we tried to probe for the PHY from the module state machine.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>