ixgbe: Change the lan_id and func fields to a u8 to avoid casts

ixgbe: Change the lan_id and func fields to a u8 to avoid casts

Since the lan_id and func fields only ever hold small values, make
them u8 to avoid casts used to silence warnings.

Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>