irqchip/gic-v3-its: Tag ITS device as shared if allocating for a proxy device

The ITS already has some notion of "shared" devices. Let's map the
MSI_ALLOC_FLAGS_PROXY_DEVICE flag onto this internal property.

Signed-off-by: Marc Zyngier <[e-mail]>
Tested-by: John Garry <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/irqchip/irq-gic-v3-its.c

···
 		goto out;
 	}
 
+	if (info->flags & MSI_ALLOC_FLAGS_PROXY_DEVICE)
+		its_dev->shared = true;
+
 	pr_debug("ITT %d entries, %d bits\n", nvec, ilog2(nvec));
 out:
 	mutex_unlock(&its->dev_alloc_lock);