net/mlx5: IPSec, fix 64-bit division correctly

The new IPSec offload code introduced a build error:

drivers/net/ethernet/mellanox/mlx5/core/en_accel/ipsec_rxtx.o: In function `mlx5e_ipsec_build_inverse_table':
ipsec_rxtx.c:(.text+0x556): undefined reference

Another patch was added on top to fix the build error, but
that introduced a new bug, as we now use the remainder of
the division rather than the result.

This makes it use the correct helper function instead.

Fixes: 5dfd87b6 ("net/mlx5: IPSec, Fix 64-bit division on 32-bit builds")
Fixes: 2ac9cfe7 ("net/mlx5e: IPSec, Add Innova IPSec offload TX data path")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Ilan Tayari <ilant@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx5/core/en_accel/ipsec_rxtx.c

@@ -363,7 +363,6 @@ void mlx5e_ipsec_build_inverse_table(void)
 {
 	u16 mss_inv;
 	u32 mss;
-	u64 n;
 
 	/* Calculate 1/x inverse table for use in GSO data path.
 	 * Using this table, we provide the IPSec accelerator with the value of
@@ -373,8 +372,7 @@ void mlx5e_ipsec_build_inverse_table(void)
 	 */
 	mlx5e_ipsec_inverse_table[1] = htons(0xFFFF);
 	for (mss = 2; mss < MAX_LSO_MSS; mss++) {
-		n = 1ULL << 32;
-		mss_inv = do_div(n, mss) >> 16;
+		mss_inv = div_u64(1ULL << 32, mss) >> 16;
 		mlx5e_ipsec_inverse_table[mss] = htons(mss_inv);
 	}
 }