audio: fix mixer path for speaker

Fix a mistake in mixer path definition for speaker.

Bug: 8272345
Change-Id: I1710ebbc88dfa695794c4bd83bd42bc4a6564765
diff --git a/mixer_paths.xml b/mixer_paths.xml
index 0d04efb..6bf95b3 100644
--- a/mixer_paths.xml
+++ b/mixer_paths.xml
@@ -227,7 +227,7 @@
         <ctl name="RX3 MIX1 INP1" value="RX1" />
         <ctl name="RX3 MIX1 INP2" value="RX6" />
         <ctl name="RX4 DSM MUX" value="DSM_INV" />
-        <ctl name="SLIM TX3 MUX" value="RMIX1" />
+        <ctl name="SLIM TX3 MUX" value="RMIX3" />
     </path>
 
     <path name="speaker-mic">