ixgbe: fix enum type mismatch on disable laser

Fixes a recent bug on the patch (c6ecf39a)
that disabled the laser on ifconfig down.  Compilers were seeing a enum
mismatch.

Signed-off-by Don Skidmore <donald.c.skidmore@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>