ixgbe: Add a second feature flags variable, move HW RSC capability there

This adds a second feature flag variable to use for future feature
expansion.  Add HW RSC to this new feature flags variable.

Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>