ext4: use LIST_HEAD() to initialize the list_head in mballoc.c

Use LIST_HEAD() to initialize the list_head instead of open-coding it.

Signed-off-by: Ruan Jinjie <ruanjinjie@huawei.com>
Link: https://lore.kernel.org/r/20230812071839.3481909-1-ruanjinjie@huawei.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>