hevc: Clip the pixel before shifting

Prevent an out of array bound read.

Fixes: asan_stack-oob_eae8e3_7333_WPP_B_ericsson_MAIN10_2.bit
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/hevcdsp_template.c

@@ -395,7 +395,7 @@ static void FUNC(sao_band_filter)(uint8_t *_dst, uint8_t *_src,
         offset_table[(k + sao_left_class) & 31] = sao_offset_val[k + 1];
     for (y = 0; y < height; y++) {
         for (x = 0; x < width; x++)
-            dst[x] = av_clip_pixel(src[x] + offset_table[av_clip_pixel(src[x] >> shift)]);
+            dst[x] = av_clip_pixel(src[x] + offset_table[av_clip_pixel(src[x]) >> shift]);
         dst += stride;
         src += stride;
     }