MIPS: Select CONFIG_HANDLE_DOMAIN_IRQ and make it work.

Per the subject, always select HANDLE_DOMAIN_IRQ, and implement
set_irq_regs() so that it actually works.
Signed-off-by: NDavid Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12496/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -62,6 +62,7 @@ config MIPS
 	select HAVE_IRQ_TIME_ACCOUNTING
 	select GENERIC_TIME_VSYSCALL
 	select ARCH_CLOCKSOURCE_DATA
+	select HANDLE_DOMAIN_IRQ
 
 menu "Machine selection"
 

arch/mips/include/asm/irq_regs.h

@@ -18,4 +18,14 @@ static inline struct pt_regs *get_irq_regs(void)
 	return current_thread_info()->regs;
 }
 
+static inline struct pt_regs *set_irq_regs(struct pt_regs *new_regs)
+{
+	struct pt_regs *old_regs;
+
+	old_regs = get_irq_regs();
+	current_thread_info()->regs = new_regs;
+
+	return old_regs;
+}
+
 #endif /* __ASM_IRQ_REGS_H */