(motion for reformation of warranty deed granted and upheld on appeal; sales contract for 176.52 acres reserved to sellers all minerals, royalties and timber interests in the land, but deed did not contain mineral reservation; lawyer who prepared sales contract and deed used title insurance commitment's legal description of property (which did not contain mineral reservation) when preparing warranty deed and did not compare deed with sales contract; scrivener's error sufficient to show mutual mistake; deed not ambiguous).