i40e: convert to cpu from le16 to generate switch_id correctly

On Big Endian platforms we would incorrectly calculate the wrong switch
id since we did not properly convert the le16 value into CPU format.
Caught by sparse.

Change-ID: I69a2f9fa064a0a91691f7d0e6fcc206adceb8e36
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>