rename sensor_t to acc_t and gyro_t and remove unused variables from

each.  relocated acc_t/gyro_t from sensors_common.h into
drivers/accgyro_common.h since they define an interface and the
dependency was pointing the wrong way from the drivers.
baro_t/acc_t/gyro_t dependences are all now pointing the right way.

src/sensors_common.h

@@ -22,16 +22,4 @@ typedef enum {
     CW270_DEG_FLIP = 8
 } sensor_align_e;
 
-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)
-    char revisionCode;                                      // a revision code for the sensor, if known
-} sensor_t;
-
 extern int16_t heading;