tests: driver_mq3: vtimer -> xtimer

tests/driver_mq3/Makefile

@@ -10,7 +10,7 @@ ifneq (,$(filter stm32f4discovery,$(BOARD)))
 endif
 
 USEMODULE += mq3
-USEMODULE += vtimer
+USEMODULE += xtimer
 
 ifneq (,$(MQ3_ADC))
   CFLAGS += -DMQ3_ADC=$(MQ3_ADC)

tests/driver_mq3/main.c

@@ -20,7 +20,7 @@
 
 #include <stdio.h>
 
-#include "vtimer.h"
+#include "xtimer.h"
 #include "mq3.h"
 #include "periph_conf.h"
 #include "periph/adc.h"
@@ -58,7 +58,7 @@ int main(void)
 
         printf("RAW: %4i, per mille: %1i.%03i\n", raw, alc_a, alc_b);
 
-        vtimer_usleep(500 * 1000);
+        xtimer_usleep(500 * 1000);
     }
     return 0;
 }