MIPS: 64-bit: Fix o32 lookup_dcookie syscall

An o32 aplication passes a 64-bit value in a pair of registers; a 64-bit
kernel expects a 64-bit argument in a single register.

Signed-off-by: Chen Jie <chenj@lemote.com>
Signed-off-by: Hu Hongbing <huhb@lemote.com>
Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>