devlink: Fix port_type_set function pointer check

Fix a typo when checking existence of port_type_set function pointer.

Fixes: 82564f6c ("devlink: Simplify devlink port API calls")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>