sound_card_init: max98397: Prevent integer overflow in RDC calibration

The `avg_rdc` accumulator in `do_rdc_calibration` was changed to
`i64` to prevent potential integer overflows when summing RDC values.

BUG=b:407129459
TEST=CQ

Change-Id: Ia49132b26e0eef13d8fb82887f1b5a1540350068
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/adhd/+/6420893
Reviewed-by: Yu-Hsuan Hsu <[email protected]>
Tested-by: [email protected] <[email protected]>
Reviewed-by: Baili Deng <[email protected]>
Commit-Queue: Baili Deng <[email protected]>
Feels: Baili Deng <[email protected]>
Tested-by: Judy Hsiao <[email protected]>
Feels: Judy Hsiao <[email protected]>
Auto-Submit: Judy Hsiao <[email protected]>

Author: judyhsiao2020

sound_card_init/amp/src/max98373d/mod.rs

@@ -372,21 +372,21 @@ impl Max98373 {
         self.set_spt_mode(SPTMode::OFF)?;
         self.set_calibration_mode(CalibMode::ON)?;
         // Playback of zeros is started, and the main thread can start the calibration.
-        let mut avg_rdc = vec![0; self.setting.num_channels()];
+        let mut avg_rdc: Vec<i64> = vec![0; self.setting.num_channels()];
         for _ in 0..Self::CALIB_REPEAT_TIMES {
             let rdc = self.get_adaptive_rdc()?;
             for i in 0..self.setting.num_channels() {
-                avg_rdc[i] += rdc[i];
+                avg_rdc[i] += rdc[i] as i64;
             }
             thread::sleep(Self::RDC_CALIB_INTERVAL);
         }
         self.set_spt_mode(SPTMode::ON)?;
         self.set_calibration_mode(CalibMode::OFF)?;
         zero_player.stop()?;
 
-        avg_rdc = avg_rdc
+        let avg_rdc: Vec<i32> = avg_rdc
             .iter()
-            .map(|val| val / Self::CALIB_REPEAT_TIMES as i32)
+            .map(|val| (val / Self::CALIB_REPEAT_TIMES as i64) as i32) // Cast back to i32 after division
             .collect();
         Ok(avg_rdc)
     }