ext4: remove unused function declaration

These functions do not have its function implementation.
So those function declaration is useless. Remove these

Signed-off-by: Cai Xinchen <caixinchen1@huawei.com>
Link: https://lore.kernel.org/r/20230802030025.173148-1-caixinchen1@huawei.com


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