MIPS: Loongson: irq.c: Misc cleanups

* Remove unnecessary 'if (int_status & (1 <<10))' statement
* s/if (foo != 0)/if (foo)/
* Remove unused 'inst_status &= ~(1 << i);' line

Signed-off-by: Shinya Kuribayashi <skuribay@pobox.com>
To: wuzhangjin@gmail.com
CC: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1433/


Acked-by: Wu Zhangjin <wuzhangjin@gmail.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>