MIPS: Loongson1B: Fix reboot problem on LS1B

- Correct the header file of watchdog registers
 - Use ioremap_nocache() to access watchdog registers instead

Signed-off-by: Kelvin Cheung <keguang.zhang@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/8022/


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