x86/platform/intel-mid: Correct MSI IRQ line for watchdog device

The interrupt line used for the watchdog is 12, according to the official
Intel Edison BSP code.

And indeed after fixing it we start getting an interrupt and thus the
watchdog starts working again:

  [  191.699951] Kernel panic - not syncing: Kernel Watchdog
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Cohen <david.a.cohen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 78a3bb9e ("x86: intel-mid: add watchdog platform code for Merrifield")
Link: http://lkml.kernel.org/r/20170312150744.45493-1-andriy.shevchenko@linux.intel.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

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

@@ -19,7 +19,7 @@
 #include <asm/intel_scu_ipc.h>
 #include <asm/io_apic.h>
 
-#define TANGIER_EXT_TIMER0_MSI 15
+#define TANGIER_EXT_TIMER0_MSI 12
 
 static struct platform_device wdt_dev = {
 	.name = "intel_mid_wdt",