ira: Fix old-reload targets [PR103974]

ira: Fix old-reload targets [PR103974]

The new IRA heuristics would need more work on old-reload targets,
since flattening needs to be able to undo the cost propagation.
It's doable, but hardly seems worth it.

This patch therefore makes all the new calls to
ira_subloop_allocnos_can_differ_p return false if !ira_use_lra_p.
The color_pass code that predated the new function (and that was
the source of ira_subloop_allocnos_can_differ_p) continues to
behave as before.

It's a hack, but at least it has the advantage that the new parameter
would become obviously unused if reload and (!)ira_use_lra_p were
removed.  The hack should therefore disappear alongside reload.

gcc/
	PR rtl-optimization/103974
	* ira-int.h (ira_subloop_allocnos_can_differ_p): Take an
	extra argument, default true, that says whether old-reload
	targets should be excluded.
	* ira-color.c (color_pass): Pass false.