fs: Move mmap callback before truncate in [file|mountpt]_operations

since mmap may exist in block_operations, but truncate may not,
moving mmap beforee truncate could make three struct more compatible

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

fs/nxffs/nxffs_initialize.c

@@ -54,12 +54,12 @@ const struct mountpt_operations nxffs_operations =
   nxffs_write,       /* write */
   NULL,              /* seek -- Use f_pos in struct file */
   nxffs_ioctl,       /* ioctl */
+  NULL,              /* mmap */
 #ifdef __NO_TRUNCATE_SUPPORT__
   nxffs_truncate,    /* truncate */
 #else
   NULL,              /* truncate */
 #endif
-  NULL,              /* mmap */
 
   NULL,              /* sync -- No buffered data */
   nxffs_dup,         /* dup */