MIPS: Loongson-3: remove deprecated IRQF_DISABLED

This removes the use of the IRQF_DISABLED flag
from arch/mips/loongson/loongson-3/hpet.c

It's a NOOP since 2.6.35.

Signed-off-by: Michael Opdenacker <michael.opdenacker@free-electrons.com>
Cc: chenhc@lemote.com
Cc: taohl@lemote.com
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/9609/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>