ext4: remove redundant check of count

Remove zero check of count which is always non-zero.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/20230826174712.4059355-7-shikemeng@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>