radeonsi/vcn: AV1 skip the redundant bs resize

For AV1, the begin bitstream buffer have included all the tile data,
and extra bitstream buffer is useless and causing the bad performance
by bs buffer resize/map/copy.

Signed-off-by: Leo Liu <leo.liu@amd.com>
Reviewed-by: Ruijing Dong <ruijing.dong@amd.com>
Reviewed-by: Veerabadhran Gopalakrishnan <veerabadhran.gopalakrishnan@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22557>

src/gallium/drivers/radeonsi/radeon_vcn_dec.c

@@ -2865,6 +2865,9 @@ static void radeon_dec_decode_bitstream(struct pipe_video_codec *decoder,
    if (!dec->bs_ptr)
       return;
 
+   if (dec->bs_size && dec->stream_type == RDECODE_CODEC_AV1)
+      return;
+
    unsigned long total_bs_size = dec->bs_size;
    for (i = 0; i < num_buffers; ++i)
       total_bs_size += sizes[i];