quota: fix wrong condition in is_quota_modification()

quota: fix wrong condition in is_quota_modification()

commit 6565c182094f69e4ffdece337d395eb7ec760efc upstream.

Quoted from
commit 3da40c7b0898 ("ext4: only call ext4_truncate when size <= isize")

" At LSF we decided that if we truncate up from isize we shouldn't trim
  fallocated blocks that were fallocated with KEEP_SIZE and are past the
 new i_size.  This patch fixes ext4 to do this. "

And generic/092 of fstest have covered this case for long time, however
is_quota_modification() didn't adjust based on that rule, so that in
below condition, we will lose to quota block change:
- fallocate blocks beyond EOF
- remount
- truncate(file_path, file_size)

Fix it.

Link: https://lore.kernel.org/r/20190911093650.35329-1-yuchao0@huawei.com
Fixes: 3da40c7b0898 ("ext4: only call ext4_truncate when size <= isize")
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>