libOpus: fix integer overflow in silk_resampler_down2_hp am: 98ec800bdf am: fd1465e039 am: bdf35d57f4 am: 25204e35d4

Original change: https://android-review.googlesource.com/c/platform/external/libopus/+/1767386

Change-Id: I107308c3fe20098b2751d5906c5af34ad402ba67