ixgbe: do not set low power mode
Orabug:
21823210
The following commit added the capability of entering low power mode:
ixgbe: Add a PHY power state method
This works fine with newer drivers that support this capability,
however older drivers that dont support this encounter a regression
as they are not able to restore power mode at boot when the driver
loads. This regression is encountered when booting a newer kernel/driver
that supports low power mode, then doing a warm reboot to an older
kernel or other OS like FreeBSD that do not know how to restore the
power mode. In this case a cold reboot is required to restore power
mode.
Signed-off-by: Brian Maly <brian.maly@oracle.com>