de-duplicate failsafe code. extract failsafe code to seperate files.

remove dependency on board.h and mw.h on a few files.

Moved rx configuration paramaters into rxConfig in order to remove the
dependency on config_t from the sbus rx code  - sumd/spektrum to follow.

Avoided use of YAW/PITCH/ROLL in some files since those constants are
from an unrelated enum type.

Replaced some magic numbers with constants to remove comments and
improve code readability.

Note, due to the tight coupling and global variable usage it was
difficult to create a smaller commit.

src/rx_common.c

@@ -0,0 +1,59 @@
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "platform.h"
+
+#include "rx_common.h"
+#include "config.h"
+
+// FIXME all includes below are just for pwmReadRawRC because it uses mcfg
+#ifdef FY90Q
+#include "drivers/pwm_fy90q.h"
+#else
+#include "drivers/pwm_common.h"
+#endif
+
+
+int16_t rcData[RC_CHANS];       // interval [1000;2000]
+
+rcReadRawDataPtr rcReadRawFunc = NULL;  // receive data from default (pwm/ppm) or additional (spek/sbus/?? receiver drivers)
+
+uint16_t pwmReadRawRC(rxConfig_t *rxConfig, uint8_t chan)
+{
+    uint16_t data;
+
+    data = pwmRead(rxConfig->rcmap[chan]);
+    if (data < 750 || data > 2250)
+        data = rxConfig->midrc;
+
+    return data;
+}
+
+void computeRC(rxConfig_t *rxConfig)
+{
+    uint8_t chan;
+
+    if (feature(FEATURE_SERIALRX)) {
+        for (chan = 0; chan < 8; chan++)
+            rcData[chan] = rcReadRawFunc(rxConfig, chan);
+    } else {
+        static int16_t rcData4Values[8][4], rcDataMean[8];
+        static uint8_t rc4ValuesIndex = 0;
+        uint8_t a;
+
+        rc4ValuesIndex++;
+        for (chan = 0; chan < 8; chan++) {
+            rcData4Values[chan][rc4ValuesIndex % 4] = rcReadRawFunc(rxConfig, chan);
+            rcDataMean[chan] = 0;
+            for (a = 0; a < 4; a++)
+                rcDataMean[chan] += rcData4Values[chan][a];
+
+            rcDataMean[chan] = (rcDataMean[chan] + 2) / 4;
+            if (rcDataMean[chan] < rcData[chan] - 3)
+                rcData[chan] = rcDataMean[chan] + 2;
+            if (rcDataMean[chan] > rcData[chan] + 3)
+                rcData[chan] = rcDataMean[chan] - 2;
+        }
+    }
+}