avcodec/golomb: Assert that k is in the supported range for get_ur/sr_golomb()

Found by code review related to CID1604563 Overflowed return value

Sponsored-by: Sovereign Tech Fund
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit b2aaeb81f6)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/golomb.h

@@ -402,6 +402,7 @@ static inline int get_ur_golomb(GetBitContext *gb, int k, int limit,
     log = av_log2(buf);
 
     if (log > 31 - limit) {
+        av_assert2(log >= k);
         buf >>= log - k;
         buf  += (30U - log) << k;
         LAST_SKIP_BITS(re, gb, 32 + k - log);