struct stat is not posix conformant on microblaze with __USE_FILE_OFFSET64

Commit a06b40cdf5 updated stat.h to use
__USE_XOPEN2K8 instead of __USE_MISC to add the st_atim, st_mtim and
st_ctim members to struct stat. However, for microblaze, there are two
definitions of struct stat, depending on the __USE_FILE_OFFSET64 macro.
The second one was not updated.

Change __USE_MISC to __USE_XOPEN2K8 in the __USE_FILE_OFFSET64 version
of struct stat for microblaze.

sysdeps/unix/sysv/linux/microblaze/bits/struct_stat.h

@@ -89,7 +89,7 @@ struct stat
         __blksize_t             st_blksize; /* Optimal block size for I/O.  */
         int                     __pad3;
         __blkcnt64_t            st_blocks;  /* Number 512-byte blocks allocated.  */
-# ifdef __USE_MISC
+# ifdef __USE_XOPEN2K8
         /* Nanosecond resolution timestamps are stored in a format
          * equivalent to 'struct timespec'. This is the type used
          * whenever possible but the Unix namespace rules do not allow the