ext4: use true,false for bool variable

Fixes coccicheck warning:

fs/ext4/extents.c:5271:6-12: WARNING: Assignment of 0/1 to bool variable
fs/ext4/extents.c:5287:4-10: WARNING: Assignment of 0/1 to bool variable

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/1577241959-138695-1-git-send-email-zhengbin13@huawei.com


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