MIPS: Loongson-3: Adjust irq dispatch to speedup processing

This patch adjust the logic in mach_irq_dispatch(), allow multiple IPs
handled in the same dispatching. This can speedup interrupt processing.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: Steven J . Hill <sjhill@realitydiluted.com>
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/12891/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>