target/file: fix inclusive vfs_fsync_range() end

Both of the file target's calls to vfs_fsync_range() got the end offset
off by one. The range is inclusive, not exclusive. It would sync a bit
more data than was required.

The sync path already tested the length of the range and fell back to
LLONG_MAX so I copied that pattern in the rw path.

This is untested. I found the errors by inspection while following other
code.

Signed-off-by: Zach Brown <[e-mail]>
Signed-off-by: Nicholas Bellinger <[e-mail]>

drivers/target/target_core_file.c

···
 	} else {
 		start = cmd->t_task_lba * dev->dev_attrib.block_size;
 		if (cmd->data_length)
-			end = start + cmd->data_length;
+			end = start + cmd->data_length - 1;
 		else
 			end = LLONG_MAX;
 	}
···
 			struct fd_dev *fd_dev = FD_DEV(dev);
 			loff_t start = cmd->t_task_lba *
 				dev->dev_attrib.block_size;
-			loff_t end = start + cmd->data_length;
+			loff_t end;
+
+			if (cmd->data_length)
+				end = start + cmd->data_length - 1;
+			else
+				end = LLONG_MAX;
 
 			vfs_fsync_range(fd_dev->fd_file, start, end, 1);
 		}