Pal: remove repeated initialization for target_sample_rate

Remove repeated initialization for target_sample_rate to
avoid samplerate in RM.xml can not overwrite requested
sample rate.

Change-Id: I44db288a8eb13bbe2bed8cebd0adc339e0399660
diff --git a/device/src/USBAudio.cpp b/device/src/USBAudio.cpp
index cb6f8ac..d15cb93 100644
--- a/device/src/USBAudio.cpp
+++ b/device/src/USBAudio.cpp
@@ -884,7 +884,6 @@
 
         if (!profile_list_ch.empty()) {
             /*3. get best Sample Rate */
-            int target_sample_rate = media_config.sample_rate;
             if (uhqa && is_playback) {
                 for (auto ch_iter = profile_list_ch.begin(); ch_iter!= profile_list_ch.end(); ++ch_iter) {
                     if ((*ch_iter)->isRateSupported(SAMPLINGRATE_192K)) {