irqchip/irq-alpine-msi: Release the correct domain on error

The "msi_domain" variable is NULL here so it leads to a NULL dereference.  It
looks like we actually intended to free "middle_domain".

Fixes: e6b78f2c3e14 ('irqchip: Add the Alpine MSIX interrupt controller')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Antoine Tenart <antoine.tenart@free-electrons.com>
Cc: kernel-janitors@vger.kernel.org
Cc: Tsahee Zidenberg <tsahee@annapurnalabs.com>
Link: http://lkml.kernel.org/r/20160311081442.GE31887@mwanda
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

drivers/irqchip/irq-alpine-msi.c

@@ -220,7 +220,7 @@ static int alpine_msix_init_domains(struct alpine_msix_data *priv,
 					       middle_domain);
 	if (!msi_domain) {
 		pr_err("Failed to create MSI domain\n");
-		irq_domain_remove(msi_domain);
+		irq_domain_remove(middle_domain);
 		return -ENOMEM;
 	}