[WATCHDOG] set max63xx driver as ARM only

Use of ioremap() causes build failure on S390.
Restrict the driver to ARM until another architecture comes along
and enables the driver for its own use.

Signed-off-by: Marc Zyngier <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

drivers/watchdog/Kconfig

···
 	  To compile this driver as a module, choose M here: the
 	  module will be called softdog.
 
-config MAX63XX_WATCHDOG
-       tristate "Max63xx watchdog"
-       help
-         Support for memory mapped max63{69,70,71,72,73,74} watchdog timer.
-
 config WM831X_WATCHDOG
 	tristate "WM831x watchdog"
 	depends on MFD_WM831X
···
 
 	  To compile this driver as a module, choose M here: the
 	  module will be called ts72xx_wdt.
+
+config MAX63XX_WATCHDOG
+	tristate "Max63xx watchdog"
+	depends on ARM
+	help
+	  Support for memory mapped max63{69,70,71,72,73,74} watchdog timer.
 
 # AVR32 Architecture