MIPS: Add IRQF_TIMER flag for timer interrupts

As the commit 3ee4c147 shows, we need to "Add IRQF_TIMER flag for timer
interrupts", Atsushi Nemoto have reported that some other timer interrupts
should be considered, Here it is.

Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>