mfd: ab8500-core: Use 'ifdef' for config options

The config symbol 'CONFIG_DEBUG_FS' should be protected by a 'ifdef' instead
of a plain 'if'.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/ab8500-core.c b/drivers/mfd/ab8500-core.c
index ce48aa7..bde2fc0 100644
--- a/drivers/mfd/ab8500-core.c
+++ b/drivers/mfd/ab8500-core.c
@@ -1754,7 +1754,7 @@
 	if (ret)
 		return ret;
 
-#if CONFIG_DEBUG_FS
+#ifdef CONFIG_DEBUG_FS
 	/* Pass to debugfs */
 	ab8500_debug_resources[0].start = ab8500->irq;
 	ab8500_debug_resources[0].end = ab8500->irq;