avcodec/jpeglsdec: Increase range for N in ls_get_code_runterm() by using unsigned

Fixes: left shift of 32768 by 16 places cannot be represented in type 'int'
Fixes: Timeout
Fixes: 44219/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SMVJPEG_fuzzer-4679455379947520
Fixes: 44088/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SMVJPEG_fuzzer-4885976600674304

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/jpeglsdec.c

@@ -191,7 +191,7 @@ static inline int ls_get_code_runterm(GetBitContext *gb, JLSState *state,
     if (RItype)
         temp += state->N[Q] >> 1;
 
-    for (k = 0; (state->N[Q] << k) < temp; k++)
+    for (k = 0; ((unsigned)state->N[Q] << k) < temp; k++)
         ;
 
 #ifdef JLS_BROKEN