ixgbe: add missing configuration for rate select 1

Add RS1 configuration to ixgbe_set_soft_rate_select_speed()

Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>