aarch64: Use real scalar op counts

aarch64: Use real scalar op counts

Now that vector finish_costs is passed the associated scalar costs,
we can record the scalar issue information while computing the scalar
costs, rather than trying to estimate it while computing the vector
costs.

This simplifies things a little, but the main motivation is to improve
accuracy.

gcc/
	* config/aarch64/aarch64.c (aarch64_vector_costs::m_scalar_ops)
	(aarch64_vector_costs::m_sve_ops): Replace with...
	(aarch64_vector_costs::m_ops): ...this.
	(aarch64_vector_costs::analyze_loop_vinfo): Update accordingly.
	(aarch64_vector_costs::adjust_body_cost_sve): Likewise.
	(aarch64_vector_costs::aarch64_vector_costs): Likewise.
	Initialize m_vec_flags here rather than in add_stmt_cost.
	(aarch64_vector_costs::count_ops): Test for scalar reductions too.
	Allow vectype to be null.
	(aarch64_vector_costs::add_stmt_cost): Call count_ops for scalar
	code too.  Don't require vectype to be nonnull.
	(aarch64_vector_costs::adjust_body_cost): Take the loop_vec_info
	and scalar costs as parameters.  Use the scalar costs to determine
	the cycles per iteration of the scalar loop, then multiply it
	by the estimated VF.
	(aarch64_vector_costs::finish_cost): Update call accordingly.