aaudio: fix callback size for Legacy input

Set the size of the callback buffer based on the device format
instead of the app format.

Bug: 149249791
Test: atest CtsNativeMediaAAudioTestCases
Change-Id: I0dc5724109a802eea15100782c18986a64e6acd2
diff --git a/media/libaaudio/src/legacy/AudioStreamLegacy.cpp b/media/libaaudio/src/legacy/AudioStreamLegacy.cpp
index 91d2eff..abc3239 100644
--- a/media/libaaudio/src/legacy/AudioStreamLegacy.cpp
+++ b/media/libaaudio/src/legacy/AudioStreamLegacy.cpp
@@ -72,7 +72,7 @@
 
 // Implement FixedBlockProcessor
 int32_t AudioStreamLegacy::onProcessFixedBlock(uint8_t *buffer, int32_t numBytes) {
-    int32_t numFrames = numBytes / getBytesPerDeviceFrame();
+    int32_t numFrames = numBytes / mBlockAdapterBytesPerFrame;
     return (int32_t) callDataCallbackFrames(buffer, numFrames);
 }