Updating accgyro files so they do not include "board.h". It is now

clear what all accgyro drivers need to compile and what was
unnecessarily included before.

src/sensors_common.h

@@ -0,0 +1,18 @@
+#pragma once
+
+typedef void (* sensorInitFuncPtr)(sensor_align_e align);   // sensor init prototype
+typedef void (* sensorReadFuncPtr)(int16_t *data);          // sensor read and align prototype
+
+typedef struct sensor_t
+{
+    sensorInitFuncPtr init;                                 // initialize function
+    sensorReadFuncPtr read;                                 // read 3 axis data function
+    sensorReadFuncPtr temperature;                          // read temperature if available
+    float scale;                                            // scalefactor (currently used for gyro only, todo for accel)
+} sensor_t;
+
+typedef enum {
+    X = 0,
+    Y,
+    Z
+} sensor_axis_e;