Fix AudioControl@2.0 fade check

Fade now checks isValidValue rather than !isValidValue

Bug: 155225937
Test: built ran and adjusted fade
Change-Id: I21b0dee8ebd677217b037c38cc744a77cf145709
diff --git a/automotive/audiocontrol/2.0/default/AudioControl.cpp b/automotive/audiocontrol/2.0/default/AudioControl.cpp
index 5bde839..b7c11cd 100644
--- a/automotive/audiocontrol/2.0/default/AudioControl.cpp
+++ b/automotive/audiocontrol/2.0/default/AudioControl.cpp
@@ -69,7 +69,7 @@
 }
 
 Return<void> AudioControl::setFadeTowardFront(float value) {
-    if (!isValidValue(value)) {
+    if (isValidValue(value)) {
         // Just log in this default mock implementation
         LOG(INFO) << "Fader set to " << value;
     } else {