rtc: change to new flag variable

Replace EXTRA_CFLAGS with ccflags-y.
Signed-off-by: matt mooney <mfm@muteddisk.com>
Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>

drivers/rtc/Makefile

@@ -2,9 +2,7 @@
 # Makefile for RTC class/drivers.
 #
 
-ifeq ($(CONFIG_RTC_DEBUG),y)
-	EXTRA_CFLAGS		+= -DDEBUG
-endif
+ccflags-$(CONFIG_RTC_DEBUG)	:= -DDEBUG
 
 obj-$(CONFIG_RTC_LIB)		+= rtc-lib.o
 obj-$(CONFIG_RTC_HCTOSYS)	+= hctosys.o