aacenc: handle input size not aligned at sample boundary

Bug: 136068046
Test: modified EncoderTest
Change-Id: Ife09efcedf573d4327e8482e03dd82fcafdb5eb2
diff --git a/media/codec2/components/aac/C2SoftAacEnc.h b/media/codec2/components/aac/C2SoftAacEnc.h
index 2655039..6ecfbdd 100644
--- a/media/codec2/components/aac/C2SoftAacEnc.h
+++ b/media/codec2/components/aac/C2SoftAacEnc.h
@@ -61,6 +61,10 @@
     bool mSignalledError;
     std::atomic_uint64_t mOutIndex;
 
+    // We support max 6 channels
+    uint8_t mRemainder[6 * sizeof(int16_t)];
+    size_t mRemainderLen;
+
     status_t initEncoder();
 
     status_t setAudioParams();