ixgbe: Drop RLPML configuration from x540 RXDCTL register configuration

Since we are doing a page based receive there is no point in setting a maximum
packet length on the x540 RXDCTL register.  As such we can drop the code from
the driver entirely.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Tested-by: Marcus Dennis <marcusx.e.dennis@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>