irqchip/gic-v3: Add GICv4.1 VPEID size discovery

While GICv4.0 mandates 16 bit worth of VPEIDs, GICv4.1 allows smaller
implementations to be built. Add the required glue to dynamically
compute the limit.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Link: https://lore.kernel.org/r/20191224111055.11836-3-maz@kernel.org
diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index ffcb018..286f982 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -1576,6 +1576,9 @@ static int __init gic_init_bases(void __iomem *dist_base,
 
 	pr_info("%d SPIs implemented\n", GIC_LINE_NR - 32);
 	pr_info("%d Extended SPIs implemented\n", GIC_ESPI_NR);
+
+	gic_data.rdists.gicd_typer2 = readl_relaxed(gic_data.dist_base + GICD_TYPER2);
+
 	gic_data.domain = irq_domain_create_tree(handle, &gic_irq_domain_ops,
 						 &gic_data);
 	irq_domain_update_bus_token(gic_data.domain, DOMAIN_BUS_WIRED);