tg3: Remove unnecessary phy reset during ethtool commands

The current code unnecessarily resets the phy when we use ethtool to
change the ring parameters or flow control settings. Remove the phy
reset.

Signed-off-by: Nithin Nayak Sujir <nsujir@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>