Filter: 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/Filter/AP_Filter.cpp

@@ -1,10 +1,12 @@
+#include "AP_Filter_config.h"
+
+#if AP_FILTER_ENABLED
+
 #include "AP_Filter.h"
 #include <AP_BoardConfig/AP_BoardConfig.h>
 #include <AP_Vehicle/AP_Vehicle_Type.h>
 #include <AP_HAL/AP_HAL_Boards.h>
 
-#if AP_FILTER_ENABLED && !APM_BUILD_TYPE(APM_BUILD_AP_Periph)
-
 extern const AP_HAL::HAL& hal;
 
 const AP_Param::GroupInfo AP_Filters::var_info[] = {
@@ -152,4 +154,4 @@ AP_Filters &filters()
 
 }
 
-#endif // AP_FILTER_ENABLED && !APM_BUILD_TYPE(APM_BUILD_AP_Periph)
+#endif // AP_FILTER_ENABLED

libraries/Filter/AP_Filter_params.cpp

@@ -1,9 +1,11 @@
+#include "AP_Filter_config.h"
+
+#if AP_FILTER_ENABLED
+
 #include "AP_Filter.h"
 #include <AP_Vehicle/AP_Vehicle_Type.h>
 #include <AP_BoardConfig/AP_BoardConfig.h>
 
-#if AP_FILTER_ENABLED && !APM_BUILD_TYPE(APM_BUILD_AP_Periph)
-
 const AP_Param::GroupInfo AP_Filter_params::var_info[] = {
 
     // @Param: TYPE
@@ -22,4 +24,4 @@ AP_Filter_params::AP_Filter_params()
     AP_Param::setup_object_defaults(this, var_info);
 }
 
-#endif // AP_FILTER_ENABLED && !APM_BUILD_TYPE(APM_BUILD_AP_Periph)
+#endif // AP_FILTER_ENABLED

libraries/Filter/AP_NotchFilter_params.cpp

@@ -1,9 +1,11 @@
+#include "AP_Filter_config.h"
+
+#if AP_FILTER_ENABLED
+
 #include "AP_Filter.h"
 #include <AP_Vehicle/AP_Vehicle_Type.h>
 #include <AP_BoardConfig/AP_BoardConfig.h>
 
-#if AP_FILTER_ENABLED && !APM_BUILD_TYPE(APM_BUILD_AP_Periph)
-
 const AP_Param::GroupInfo AP_NotchFilter_params::var_info[] = {
   
     // @Param: NOTCH_FREQ
@@ -50,4 +52,4 @@ bool AP_NotchFilter_params::setup_notch_filter(NotchFilterFloat& filter, float s
     return true;
 }
 
-#endif // AP_FILTER_ENABLED && !APM_BUILD_TYPE(APM_BUILD_AP_Periph)
+#endif // AP_FILTER_ENABLED