#1021 Corrects previous implementation of dot-product filtering using Math.fma() (#1025)

Co-authored-by: Denny <denny@denny-desktop>

src/main/java/io/github/dsheirer/dsp/filter/fir/real/RealFIRFilter2.java

@@ -85,8 +85,7 @@ public class RealFIRFilter2 extends FIRFilter
         //Use vector dot product to leverage SIMD intrinsics
         for(int x = 0; x < mCoefficients.length; x++)
         {
-            //Note: Math.fma() is 2.5x faster than explicit multiply then accumulate
-            Math.fma(mData[x], mCoefficients[x], mAccumulator);
+            mAccumulator = Math.fma(mData[x], mCoefficients[x], mAccumulator);
         }
 
         /* Apply gain and return the filtered value */