btrfs: stop printing condition result in assertion failure messages

btrfs: stop printing condition result in assertion failure messages

It's useless to print the result of the condition, it's always 0 if the
assertion is triggered, so it doesn't provide any useful information.

Examples:

   assertion failed: cb->bbio.bio.bi_iter.bi_size == disk_num_bytes :: 0, in inode.c:9991
   assertion failed: folio_test_writeback(folio) :: 0, in subpage.c:476

So stop printing that, it's always ":: 0" for any assertion triggered
(except for conditions that are just an identifier).

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>