amd-xgbe-phy: On suspend, save CTRL1 reg for use on resume

Reads to registers are undefined when the PCS is powered down. To be
safe, save the CTRL1 register used for power down during suspend and
restore that value during resume.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>