i40e: Remove unneeded conversion

Remove LE16 to CPU endianes conversion from i40e_read_nvm_word_srctl
function, as it's already done by register read function.

Change-ID: I739f0f20a9b8e18223e54c0ca5443e63d75da878
Signed-off-by: Kamil Krawczyk <kamil.krawczyk@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>