ixgbe: check for WoL support in single function

ixgbe: check for WoL support in single function

This patch consolidates the case logic for checking whether a device supports
WoL into a single place. Previously ethtool and probe used similar logic that
was copied and maintained separately. This patch encapsulates the core logic
into a function so that a user only has to update one place.

Signed-off-by: Jacob Keller <[email protected]>
Tested-by: Stephen Ko <[email protected]>
Signed-off-by: Jeff Kirsher <[email protected]>