ixgbe: Fix module_param allow_unsupported_sfp type

The module_param allow_unsupported_sfp should be a boolean to match the
type in the ixgbe_hw struct.

Signed-off-by: Jeff Daly <jeffd@silicom-usa.com>
Tested-by: Gurucharan <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>