genirq: Provide irq_force_affinity fallback for non-SMP

commit 4c88d7f9 upstream.

Patch 01f8fa4f "genirq: Allow forcing cpu affinity of interrupts" added
an irq_force_affinity() function, and 30ccf03b "clocksource: Exynos_mct:
Use irq_force_affinity() in cpu bringup" subsequently uses it. However, the
driver can be used with CONFIG_SMP disabled, but the function declaration
is only available for CONFIG_SMP, leading to this build error:

drivers/clocksource/exynos_mct.c:431:3: error: implicit declaration of function 'irq_force_affinity' [-Werror=implicit-function-declaration]
   irq_force_affinity(mct_irqs[MCT_L0_IRQ + cpu], cpumask_of(cpu));

This patch introduces a dummy helper function for the non-SMP case
that always returns success, to get rid of the build error.
Since the patches causing the problem are marked for stable backports,
this one should be as well.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Link: http://lkml.kernel.org/r/5619084.0zmrrIUZLV@wuerfelSigned-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

include/linux/interrupt.h

@@ -267,6 +267,11 @@ static inline int irq_set_affinity(unsigned int irq, const struct cpumask *m)
 	return -EINVAL;
 }
 
+static inline int irq_force_affinity(unsigned int irq, const struct cpumask *cpumask)
+{
+	return 0;
+}
+
 static inline int irq_can_set_affinity(unsigned int irq)
 {
 	return 0;