Adjust inner loop cost scaling

Adjust inner loop cost scaling

This makes use of the estimated number of iterations of the inner loop
to limit --param vect-inner-loop-cost-factor scaling.  It also reduces
the maximum value of vect-inner-loop-cost-factor to 10000 making it
less likely to cause overflow of costs.

2021-08-23  Richard Biener  <rguenther@suse.de>

	* doc/invoke.texi (vect-inner-loop-cost-factor): Adjust.
	* params.opt (--param vect-inner-loop-cost-factor): Adjust
	maximum value.
	* tree-vect-loop.c (vect_analyze_loop_form): Initialize
	inner_loop_cost_factor to the minimum of the estimated number
	of iterations of the inner loop and vect-inner-loop-cost-factor.