AP_HAL_ChibiOS: correct AP_Filter defines

- checking the build type is very rarely used and definitely not required here
 - fix boilerplate to conform to normal pattern of including the config header and #if'ing based on the _ENABLED directly after that

libraries/AP_HAL_ChibiOS/hwdef/scripts/defaults_periph.h

@@ -388,3 +388,7 @@
 #ifndef AP_ICENGINE_ENABLED
 #define AP_ICENGINE_ENABLED 0
 #endif
+
+#ifndef AP_FILTER_ENABLED
+#define AP_FILTER_ENABLED 0
+#endif