avformat/mxfdec: Don't pretend array to be bigger than it is

mxf_match_uid() accepts two const UID and a len parameter.
UID is a typedef for an array of 16 uint8_t, so the const UID
parameter is actually a pointer to const uint8_t.

The point of mxf_match_uid() is to check whether the initial
part of two UIDs match; the length of said part is given
by the len parameter. Once an incomplete UID has been passed
to mxf_match_uid() (albeit with the correct len, so safe),
which makes GCC emit -Wstringop-overread warnings.

Fix this by using a const uint8_t[] as type; it is more
natural for incomplete UIDs.

Reviewed-by: Tomas Härdin <git@haerdin.se>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavformat/mxfdec.c

@@ -1544,11 +1544,11 @@ static int mxf_read_tagged_value(void *arg, AVIOContext *pb, int tag, int size,
  * Match an uid independently of the version byte and up to len common bytes
  * Returns: boolean
  */
-static int mxf_match_uid(const UID key, const UID uid, int len)
+static int mxf_match_uid(const UID key, const uint8_t uid_prefix[], int len)
 {
     int i;
     for (i = 0; i < len; i++) {
-        if (i != 7 && key[i] != uid[i])
+        if (i != 7 && key[i] != uid_prefix[i])
             return 0;
     }
     return 1;