avutil/common: Fix underflow for ROUNDED_DIV with unsigned integer

When used ROUNDED_DIV(a,b), if a is unsigned integer zero, it's
will lead to an underflow issue(it called unsigned integer
wrapping).

Fixes #8062
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Mengye Lv <mengyelv@tencent.com>
Signed-off-by: Jun Zhao <barryjzhao@tencent.com>

libavutil/common.h

@@ -53,7 +53,7 @@
 //rounded division & shift
 #define RSHIFT(a,b) ((a) > 0 ? ((a) + ((1<<(b))>>1))>>(b) : ((a) + ((1<<(b))>>1)-1)>>(b))
 /* assume b>0 */
-#define ROUNDED_DIV(a,b) (((a)>0 ? (a) + ((b)>>1) : (a) - ((b)>>1))/(b))
+#define ROUNDED_DIV(a,b) (((a)>=0 ? (a) + ((b)>>1) : (a) - ((b)>>1))/(b))
 /* Fast a/(1<<b) rounded toward +inf. Assume a>=0 and b>=0 */
 #define AV_CEIL_RSHIFT(a,b) (!av_builtin_constant_p(b) ? -((-(a)) >> (b)) \
                                                        : ((a) + (1<<(b)) - 1) >> (b))