cscd: use negative error values to indicate decode_init() failures.

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org

libavcodec/cscd.c

@@ -228,7 +228,7 @@ static av_cold int decode_init(AVCodecContext *avctx) {
             av_log(avctx, AV_LOG_ERROR,
                    "CamStudio codec error: invalid depth %i bpp\n",
                    avctx->bits_per_coded_sample);
-            return 1;
+            return AVERROR_INVALIDDATA;
     }
     c->bpp = avctx->bits_per_coded_sample;
     c->pic.data[0] = NULL;
@@ -241,7 +241,7 @@ static av_cold int decode_init(AVCodecContext *avctx) {
     c->decomp_buf = av_malloc(c->decomp_size + AV_LZO_OUTPUT_PADDING);
     if (!c->decomp_buf) {
         av_log(avctx, AV_LOG_ERROR, "Can't allocate decompression buffer.\n");
-        return 1;
+        return AVERROR(ENOMEM);
     }
     return 0;
 }