cmd/compile: remove unused isIntOrdering method

[AlphaHot]

go/src/cmd/compile/internal/gc/walk.go

Lines 3530 to 3538 in d467f3b

	// isIntOrdering reports whether n is a <, ≤, >, or ≥ ordering between integers.
	func (n *Node) isIntOrdering() bool {
	switch n.Op {
	case OLE, OLT, OGE, OGT:
	default:
	return false
	}
	return n.Left.Type.IsInteger() && n.Right.Type.IsInteger()
	}

[ianlancetaylor]

CC @mundaym

[gopherbot]

Change https://golang.org/cl/224777 mentions this issue: cmd/compile: remove unused isIntOrdering method