mfd: add #ifdef CONFIG_DEBUG_FS guard for ab8500_debug_resources

Fix below build warning if CONFIG_DEBUG_FS is disabled.

  CC      drivers/mfd/ab8500-core.o
drivers/mfd/ab8500-core.c:623: warning: 'ab8500_debug_resources' defined but not used
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/ab8500-core.c

@@ -620,6 +620,7 @@ static struct resource __devinitdata ab8500_fg_resources[] = {
 
 static struct resource __devinitdata ab8500_chargalg_resources[] = {};
 
+#ifdef CONFIG_DEBUG_FS
 static struct resource __devinitdata ab8500_debug_resources[] = {
 	{
 		.name	= "IRQ_FIRST",
@@ -634,6 +635,7 @@ static struct resource __devinitdata ab8500_debug_resources[] = {
 		.flags	= IORESOURCE_IRQ,
 	},
 };
+#endif
 
 static struct resource __devinitdata ab8500_usb_resources[] = {
 	{