mlx4_core: Fix warning from min()

Recent cpumask changes changed num_possible_cpus() from returning an int
to returning an unsigned int.  This means that doing

    min(num_possible_cpus(), <int expression>)

now produces a warning like

    drivers/net/mlx4/main.c: In function 'mlx4_enable_msi_x':
    drivers/net/mlx4/main.c:915: warning: comparison of distinct pointer types lacks a cast

Fix this by using min_t(int, ...).
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/net/mlx4/main.c

@@ -912,7 +912,7 @@ static void mlx4_enable_msi_x(struct mlx4_dev *dev)
 	int i;
 
 	if (msi_x) {
-		nreq = min(dev->caps.num_eqs - dev->caps.reserved_eqs,
+		nreq = min_t(int, dev->caps.num_eqs - dev->caps.reserved_eqs,
 			     num_possible_cpus() + 1);
 		entries = kcalloc(nreq, sizeof *entries, GFP_KERNEL);
 		if (!entries)