Make compute_operand2_range a leaf call.

Make compute_operand2_range a leaf call.

Rather than creating long call chains, put the onus for finishing
the evlaution on the caller.

	* gimple-range-gori.cc (compute_operand_range): After calling
	compute_operand2_range, recursively call self if needed.
	(compute_operand2_range): Turn into a leaf function.
	(gori_compute::compute_operand1_and_operand2_range): Finish
	operand2 calculation.
	* gimple-range-gori.h (compute_operand2_range): Remove name param.