ixgbe: rename wol_supported to more fitting wol_enabled

ixgbe: rename wol_supported to more fitting wol_enabled

The variable wol_supported really is just checking whether it is enabled, rather
than whether it is supported. If it is enabled it will be supported, but this
does not necessarily hold true the other way around. This patch renames the
variable to avoid confusion.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>