Using a cross-compiler to fix another issue, the following build error
occurred for mips defconfig:

  arch/mips/fw/arc/misc.c: In function 'ArcHalt':
  arch/mips/fw/arc/misc.c:25:2: error: implicit declaration of function 'local_irq_disable'

Fix it up by including irqflags.h.
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>