core: unified preprocessor test format

This will ease parsing for cube drivers addition

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>

Author: fpistm

cores/arduino/stm32/stm32_def.h

@@ -22,7 +22,7 @@
 
 #define USE_HAL_DRIVER
 
-#ifdef STM32F0xx
+#if defined(STM32F0xx)
   #include "stm32f0xx.h"
 #elif defined(STM32F1xx)
   #include "stm32f1xx.h"