Remove back-and-forth float to int to float conversion in acceleratio…

…n calculation (betaflight#13158)

Remove float to int to float conversion in acceleration calculation

src/main/sensors/acceleration.c

@@ -79,7 +79,7 @@ void accUpdate(timeUs_t currentTimeUs)
     applyAccelerationTrims(accelerationRuntime.accelerationTrims);
 
     for (int axis = 0; axis < XYZ_AXIS_COUNT; axis++) {
-        const int16_t val = acc.accADC[axis];
+        const float val = acc.accADC[axis];
         acc.accADC[axis] = accelerationRuntime.accLpfCutHz ? pt2FilterApply(&accelerationRuntime.accFilter[axis], val) : val;
     }
 }