ntb: intel: fix return value for ndev_vec_mask()

ndev_vec_mask() should be returning u64 mask value instead of int.
Otherwise the mask value returned can be incorrect for larger
vectors.

Fixes: e26a5843f7f5 ("NTB: Split ntb_hw_intel and ntb_transport drivers")

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Tested-by: Lucas Van <lucas.van@intel.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>

drivers/ntb/hw/intel/ntb_hw_gen1.c

@@ -265,7 +265,7 @@ static inline int ndev_db_clear_mask(struct intel_ntb_dev *ndev, u64 db_bits,
 	return 0;
 }
 
-static inline int ndev_vec_mask(struct intel_ntb_dev *ndev, int db_vector)
+static inline u64 ndev_vec_mask(struct intel_ntb_dev *ndev, int db_vector)
 {
 	u64 shift, mask;