Btrfs: use late_initcall instead of module_init

It seems that when init_btrfs_fs() is called, crc32c/crc32c-intel might
not always be already initialized, which results in the call to crypto_alloc_shash()
returning -ENOENT, as experienced by Ahmet who reported this.

Therefore make sure init_btrfs_fs() is called after crc32c is initialized (which
is at initialization level 6, module_init), by using late_initcall (which is at
initialization level 7) instead of module_init for btrfs.
Reported-and-Tested-by: Ahmet Inan <ainan@mathematik.uni-freiburg.de>
Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/super.c

@@ -1996,7 +1996,7 @@ static void __exit exit_btrfs_fs(void)
 	btrfs_hash_exit();
 }
 
-module_init(init_btrfs_fs)
+late_initcall(init_btrfs_fs);
 module_exit(exit_btrfs_fs)
 
 MODULE_LICENSE("GPL");