ext4: add missing braces in ext4_ext_drop_refs()

For clarity, add braces to the loop in ext4_ext_drop_refs().

Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20191231180444.46586-9-ebiggers@kernel.org


Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
Reviewed-by: Jan Kara <jack@suse.cz>