drivers/rtc/ds3231.c: fix GCC 4.6 build warnings

Fix:
ds3231.c: In function 'rtc_get':
ds3231.c:90:52: warning: variable 'control' set but not used
[-Wunused-but-set-variable]

Fix is done by switching to standard debug() instead of custom macro.

Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/drivers/rtc/ds3231.c b/drivers/rtc/ds3231.c
index 134a0e4..ae59cfb 100644
--- a/drivers/rtc/ds3231.c
+++ b/drivers/rtc/ds3231.c
@@ -35,16 +35,6 @@
 
 #if defined(CONFIG_CMD_DATE)
 
-/*---------------------------------------------------------------------*/
-#undef DEBUG_RTC
-
-#ifdef DEBUG_RTC
-#define DEBUGR(fmt,args...) printf(fmt ,##args)
-#else
-#define DEBUGR(fmt,args...)
-#endif
-/*---------------------------------------------------------------------*/
-
 /*
  * RTC register addresses
  */
@@ -99,7 +89,7 @@
 	mon_cent = rtc_read (RTC_MON_REG_ADDR);
 	year = rtc_read (RTC_YR_REG_ADDR);
 
-	DEBUGR ("Get RTC year: %02x mon/cent: %02x mday: %02x wday: %02x "
+	debug("Get RTC year: %02x mon/cent: %02x mday: %02x wday: %02x "
 		"hr: %02x min: %02x sec: %02x control: %02x status: %02x\n",
 		year, mon_cent, mday, wday, hour, min, sec, control, status);
 
@@ -121,7 +111,7 @@
 	tmp->tm_yday = 0;
 	tmp->tm_isdst= 0;
 
-	DEBUGR ("Get DATE: %4d-%02d-%02d (wday=%d)  TIME: %2d:%02d:%02d\n",
+	debug("Get DATE: %4d-%02d-%02d (wday=%d)  TIME: %2d:%02d:%02d\n",
 		tmp->tm_year, tmp->tm_mon, tmp->tm_mday, tmp->tm_wday,
 		tmp->tm_hour, tmp->tm_min, tmp->tm_sec);
 
@@ -136,7 +126,7 @@
 {
 	uchar century;
 
-	DEBUGR ("Set DATE: %4d-%02d-%02d (wday=%d)  TIME: %2d:%02d:%02d\n",
+	debug("Set DATE: %4d-%02d-%02d (wday=%d)  TIME: %2d:%02d:%02d\n",
 		tmp->tm_year, tmp->tm_mon, tmp->tm_mday, tmp->tm_wday,
 		tmp->tm_hour, tmp->tm_min, tmp->tm_sec);