btrfs: tree-checker: fix the wrong output of data backref objectid

[BUG]
There are some reports about invalid data backref objectids, the report
looks like this:

BTRFS critical (device sda): corrupt leaf: block=333654787489792 slot=110 extent bytenr=333413935558656 len=65536 invalid data ref objectid value 2543

The data ref objectid is the inode number inside the subvolume.

But in above case, the value is completely sane, not really showing the
problem.

[CAUSE]
The root cause of the problem is the deprecated feature, inode cache.

This feature results a special inode number, -12ULL, and it's no longer
recognized by tree-checker, triggering the error.

The direct problem here is the output of data ref objectid. The value
shown is in fact the dref_root (subvolume id), not the dref_objectid
(inode number).

[FIX]
Fix the output to use dref_objectid instead.

Reported-by: Neil Parton <[e-mail]>
Reported-by: Archange <[e-mail]>
Link: https://lore.kernel.org/linux-btrfs/CAAYHqBbrrgmh6UmW3ANbysJX9qG9Pbg3ZwnKsV=[e-mail]/
Link: https://lore.kernel.org/linux-btrfs/[e-mail]/
Fixes: f333a3c7e832 ("btrfs: tree-checker: validate dref root and objectid")
CC: [e-mail] # 6.11
Reviewed-by: Filipe Manana <[e-mail]>
Signed-off-by: Qu Wenruo <[e-mail]>
Reviewed-by: David Sterba <[e-mail]>
Signed-off-by: David Sterba <[e-mail]>

fs/btrfs/tree-checker.c

···
 				     dref_objectid > BTRFS_LAST_FREE_OBJECTID)) {
 				extent_err(leaf, slot,
 					   "invalid data ref objectid value %llu",
-					   dref_root);
+					   dref_objectid);
 				return -EUCLEAN;
 			}
 			if (unlikely(!IS_ALIGNED(dref_offset,