irqchip: gic: Don't complain in gic_get_cpumask() if UP system

In a uniprocessor implementation the interrupt processor targets
registers are read-as-zero/write-ignored (RAZ/WI). Unfortunately
gic_get_cpumask() will print a critical message saying

 GIC CPU mask not found - kernel will fail to boot.

if these registers all read as zero, but there won't actually be
a problem on uniprocessor systems and the kernel will boot just
fine. Skip this check if we're running a UP kernel or if we
detect that the hardware only supports a single processor.

Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Felipe Balbi <balbi@ti.com>
Acked-by: Nishanth Menon <nm@ti.com>
Acked-by: Stefan Agner <stefan@agner.ch>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Link: https://lkml.kernel.org/r/1426141291-21641-1-git-send-email-sboyd@codeaurora.org
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

drivers/irqchip/irq-gic.c

@@ -349,7 +349,7 @@ static u8 gic_get_cpumask(struct gic_chip_data *gic)
 			break;
 	}
 
-	if (!mask)
+	if (!mask && num_possible_cpus() > 1)
 		pr_crit("GIC CPU mask not found - kernel will fail to boot.\n");
 
 	return mask;