The mtx-1_wdt driver does not need the au1000.h header file.
Instead, the header file causes build errors, so drop it.

This change fixes multiple build errors, all in au1000.h. E.g.:

In file included from ../drivers/watchdog/mtx-1_wdt.c:44:
../arch/mips/include/asm/mach-au1x00/au1000.h: In function 'alchemy_rdsys':
../arch/mips/include/asm/mach-au1x00/au1000.h:603:36: error: implicit declaration of function 'KSEG1ADDR'; did you mean 'CKSEG1ADDR'? [-Werror=implicit-function-declaration]
  603 |  void __iomem *b = (void __iomem *)KSEG1ADDR(AU1000_SYS_PHYS_ADDR);
../arch/mips/include/asm/mach-au1x00/au1000.h:603:20: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
  603 |  void __iomem *b = (void __iomem *)KSEG1ADDR(AU1000_SYS_PHYS_ADDR);

Fixes: da2a68b3 ("watchdog: Enable COMPILE_TEST where possible")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Wim Van Sebroeck <wim@linux-watchdog.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: linux-watchdog@vger.kernel.org
Cc: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20210516211703.25349-1-rdunlap@infradead.orgSigned-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>