add parens to MAIN_FW_SIZE definition

to avoid messing up calculations

config/common_config.h

@@ -65,7 +65,7 @@
 #define USER_FLASH_LAST_PAGE_ADDRESS  0x08060000
 #define USER_FLASH_END_ADDRESS        0x0807FFFF
 #define USER_FLASH_CRC_ADDRESS        0x0807FFFC
-#define MAIN_FW_SIZE    USER_FLASH_END_ADDRESS - USER_FLASH_FIRST_PAGE_ADDRESS + 1
+#define MAIN_FW_SIZE (USER_FLASH_END_ADDRESS - USER_FLASH_FIRST_PAGE_ADDRESS + 1)
 
 #define IAP_FLASH_FIRST_PAGE_ADDRESS  0x08000000 /* Only as example see comment */
 #define IAP_FLASH_CRC_ADDRESS         0x0801FFFC