x86/platform/intel-mid: Move watchdog registration to arch_initcall()

There is no need to choose a random initcall level for certainly
architecture dependent code.

Move watchdog registration to arch_initcall() from rootfs_initcall().
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: http://lkml.kernel.org/r/20170119192425.189899-5-andriy.shevchenko@linux.intel.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/platform/intel-mid/device_libs/platform_mrfld_wdt.c

@@ -82,4 +82,4 @@ static int __init register_mid_wdt(void)
 
 	return 0;
 }
-rootfs_initcall(register_mid_wdt);
+arch_initcall(register_mid_wdt);