ixgbe: cleanup unnecessary return value in ixgbe_cache_ring_rss

This change is just to cleanup some confusing logic in ixgbe_cache_ring_rss
which can be simplified by adding a conditional with return to the start of
the call.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>