libhevc: Fix asan issue in intra pred mode assembly function

chroma intra pred 3_to_9 mode av8 assembly loads 16 bytes ahead of base
address of intermediate buffer but doesnt use it. Allocate this
additional size and offset the same to avoid access violation

Test: hevcenc -c vid_enc_cfg.txt --input selfie_1280_720.yuv --src_width 512 --src_height 512

Bug: 144595488

Change-Id: I1094cf4593ba379354f567876288e2d9b9fae83d
1 file changed