hevc: make pps/sps ids unsigned where necessary

Fixes integer overflow and out of array accesses.
Found-by: Mateusz j00ru Jurczyk and Gynvael Coldwind

libavcodec/hevc.h

@@ -463,7 +463,7 @@ typedef struct HEVCSPS {
 } HEVCSPS;
 
 typedef struct HEVCPPS {
-    int sps_id; ///< seq_parameter_set_id
+    unsigned int sps_id; ///< seq_parameter_set_id
 
     uint8_t sign_data_hiding_flag;
 

libavcodec/hevc_ps.c

@@ -610,7 +610,7 @@ int ff_hevc_decode_nal_sps(HEVCContext *s)
     const AVPixFmtDescriptor *desc;
     GetBitContext *gb = &s->HEVClc.gb;
     int ret = 0;
-    int sps_id = 0;
+    unsigned int sps_id = 0;
     int log2_diff_max_min_transform_block_size;
     int bit_depth_chroma, start, vui_present, sublayer_ordering_info;
     int i;
@@ -989,7 +989,7 @@ int ff_hevc_decode_nal_pps(HEVCContext *s)
     int log2_diff_ctb_min_tb_size;
     int i, j, x, y, ctb_addr_rs, tile_id;
     int ret = 0;
-    int pps_id = 0;
+    unsigned int pps_id = 0;
 
     AVBufferRef *pps_buf;
     HEVCPPS *pps = av_mallocz(sizeof(*pps));