avcodec/bmp_parser: Fix remaining size

Fixes part of ticket 5598

Signed-off-by: Michael Niedermayer <[email protected]>
diff --git a/libavcodec/bmp_parser.c b/libavcodec/bmp_parser.c
index c9fe153..8111ada 100644
--- a/libavcodec/bmp_parser.c
+++ b/libavcodec/bmp_parser.c
@@ -63,7 +63,7 @@
                     continue;
                 }
                 bpc->pc.frame_start_found++;
-                bpc->remaining_size = bpc->fsize + FFMAX(i - 17, 0);
+                bpc->remaining_size = bpc->fsize + i - 17;
 
                 if (bpc->pc.index + i > 17) {
                     next = i - 17;