avcodec/mjpegdec: Add YUVA420 formats to *scale asserts

Fixes assertion failure
Fixes: signal_sigabrt_7ffff6ac7bb9_2042_cov_2593130068_ef1f8a057bb6056674fad92f6b8c0acd.jpg
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mjpegdec.c

@@ -2115,6 +2115,8 @@ the_end:
                    avctx->pix_fmt == AV_PIX_FMT_YUVJ420P ||
                    avctx->pix_fmt == AV_PIX_FMT_YUV420P  ||
                    avctx->pix_fmt == AV_PIX_FMT_YUV420P16||
+                   avctx->pix_fmt == AV_PIX_FMT_YUVA420P  ||
+                   avctx->pix_fmt == AV_PIX_FMT_YUVA420P16||
                    avctx->pix_fmt == AV_PIX_FMT_GBRP     ||
                    avctx->pix_fmt == AV_PIX_FMT_GBRAP
                   );
@@ -2156,6 +2158,8 @@ the_end:
                    avctx->pix_fmt == AV_PIX_FMT_YUV440P  ||
                    avctx->pix_fmt == AV_PIX_FMT_YUVJ440P ||
                    avctx->pix_fmt == AV_PIX_FMT_YUVA444P ||
+                   avctx->pix_fmt == AV_PIX_FMT_YUVA420P  ||
+                   avctx->pix_fmt == AV_PIX_FMT_YUVA420P16||
                    avctx->pix_fmt == AV_PIX_FMT_GBRP     ||
                    avctx->pix_fmt == AV_PIX_FMT_GBRAP
                    );