ext4: remove 'needed' in trace_ext4_discard_preallocations

As 'needed' to trace_ext4_discard_preallocations is always 0 which
is meaningless. Just remove it.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20240105092102.496631-10-shikemeng@huaweicloud.com


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