MIPS: OCTEON: irq: Fix octeon_irq_force_ciu_mapping()

For irq_domain_associate() to work the virq descriptor has to be
pre-allocated in advance. Otherwise the following happens:

WARNING: CPU: 0 PID: 0 at .../kernel/irq/irqdomain.c:527 irq_domain_associate+0x298/0x2e8
error: virq128 is not allocated
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.19.78-... #1
        ...
Call Trace:
[<ffffffff801344c4>] show_stack+0x9c/0x130
[<ffffffff80769550>] dump_stack+0x90/0xd0
[<ffffffff801576d0>] __warn+0x118/0x130
[<ffffffff80157734>] warn_slowpath_fmt+0x4c/0x70
[<ffffffff801b83c0>] irq_domain_associate+0x298/0x2e8
[<ffffffff80a43bb8>] octeon_irq_init_ciu+0x4c8/0x53c
[<ffffffff80a76cbc>] of_irq_init+0x1e0/0x388
[<ffffffff80a452cc>] init_IRQ+0x4c/0xf4
[<ffffffff80a3cc00>] start_kernel+0x404/0x698

Use irq_alloc_desc_at() to avoid the above problem.
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/cavium-octeon/octeon-irq.c

@@ -127,6 +127,16 @@ static void octeon_irq_free_cd(struct irq_domain *d, unsigned int irq)
 static int octeon_irq_force_ciu_mapping(struct irq_domain *domain,
 					int irq, int line, int bit)
 {
+	struct device_node *of_node;
+	int ret;
+
+	of_node = irq_domain_get_of_node(domain);
+	if (!of_node)
+		return -EINVAL;
+	ret = irq_alloc_desc_at(irq, of_node_to_nid(of_node));
+	if (ret < 0)
+		return ret;
+
 	return irq_domain_associate(domain, irq, line << 6 | bit);
 }