Can't restore disabled iPhone because not enough disk space
When connecting it to iTunes, I would choose to set it up as a new device, rather than restoring from a backup.

Once you've done that then do the restore on your iPhone from the backup you wanted to use.

NOTE: Ensure that you do not do a new backup of your iPhone 4s before doing the restore. You may want to make a backup of your iPhone 4s backup before you begin, just in case. If you're not sure of where the backups are located, refer to this article.