testsuite: scev: expect fail on ilp32

testsuite: scev: expect fail on ilp32

I've recently patched scev-3.c and scev-5.c because it only passed by
accident on ia32.  It also fails on some (but not all) arm-eabi
variants.  It seems hard to characterize the conditions in which the
optimization is supposed to pass, but expecting them to fail on ilp32
targets, though probably a little excessive and possibly noisy, is not
quite as alarming as getting a fail in test reports, so I propose
changing the xfail marker from ia32 to ilp32.

I'm also proposing to add a similar marker to scev-4.c.  Though it
doesn't appear to be failing for me, I've got reports that suggest it
still does for others, and it certainly did for us as well.

for  gcc/testsuite/ChangeLog

	* gcc.dg/tree-ssa/scev-3.c: xfail on all ilp32 targets,
	though some of these do pass.
	* gcc.dg/tree-ssa/scev-4.c: Likewise.
	* gcc.dg/tree-ssa/scev-5.c: Likewise.