sh: intc: userimask support.

This adds support for hardware-assisted userspace irq masking for
special priority levels. Due to the SR.IMASK interactivity, only some
platforms implement this in hardware (including but not limited to
SH-4A interrupt controllers, and ARM-based SH-Mobile CPUs). Each CPU
needs to wire this up on its own, for now only SH7786 is wired up as an
example.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

include/linux/sh_intc.h

@@ -99,6 +99,15 @@ struct intc_desc symbol __initdata = {					\
 int __init register_intc_controller(struct intc_desc *desc);
 int intc_set_priority(unsigned int irq, unsigned int prio);
 
+#ifdef CONFIG_INTC_USERIMASK
+int register_intc_userimask(unsigned long addr);
+#else
+static inline int register_intc_userimask(unsigned long addr)
+{
+	return 0;
+}
+#endif
+
 int reserve_irq_vector(unsigned int irq);
 void reserve_irq_legacy(void);