fm10k: Align Rx buffers to 512B blocks

While reviewing the i40e driver changes to support page based receive I
realized that I had overlooked the fact that the fm10k hardware required a
512 byte alignment for Rx buffers.  This patch is meant to address that by
changing the alignment for Rx buffers to 512 bytes instead of allowing it
to be L1 cache aligned.

Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Tested-by: Krishneil Singh <Krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>