avformat/mov: base pcmC endianness on just the LSB

As per 23003-5:2020, the rest of the bits are reserved, and thus
in the future they may be utilized for something else.

Quote:
format_flags is a field of flags that modify the default PCM sample format.
Undefined flags are reserved and shall be zero. The following flag is defined:
  0x01 indicates little-endian format. If not present, big-endian format is used.

libavformat/mov.c

@@ -1608,7 +1608,7 @@ static int mov_read_pcmc(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     }
 
     format_flags = avio_r8(pb);
-    if (format_flags == 1) // indicates little-endian format. If not present, big-endian format is used
+    if (format_flags & 1) // indicates little-endian format. If not present, big-endian format is used
         set_last_stream_little_endian(c->fc);
 
     return 0;