net/mlx4: Use cpumask_available for eq->affinity_mask

Clang warns that the address of a pointer will always evaluated as true
in a boolean context:

drivers/net/ethernet/mellanox/mlx4/eq.c:243:11: warning: address of
array 'eq->affinity_mask' will always evaluate to 'true'
[-Wpointer-bool-conversion]
        if (!eq->affinity_mask || cpumask_empty(eq->affinity_mask))
            ~~~~~^~~~~~~~~~~~~
1 warning generated.

Use cpumask_available, introduced in commit f7e30f01a9e2 ("cpumask: Add
helper cpumask_available()"), which does the proper checking and avoids
this warning.

Link: https://github.com/ClangBuiltLinux/linux/issues/86
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/eq.c

@@ -240,7 +240,8 @@ static void mlx4_set_eq_affinity_hint(struct mlx4_priv *priv, int vec)
 	struct mlx4_dev *dev = &priv->dev;
 	struct mlx4_eq *eq = &priv->eq_table.eq[vec];
 
-	if (!eq->affinity_mask || cpumask_empty(eq->affinity_mask))
+	if (!cpumask_available(eq->affinity_mask) ||
+	    cpumask_empty(eq->affinity_mask))
 		return;
 
 	hint_err = irq_set_affinity_hint(eq->irq, eq->affinity_mask);