[testsuites] Update several scev/IVOPTs cases

[testsuites] Update several scev/IVOPTs cases

Several scev/IVOPTs cases aim to check some array references are sceved and
later marked as REFERENCE ADDRESS IV groups. With IV group type dumping
improving, these check strings can be improved. Otherwise, they become fragile
with dumping changes.

This patch is to keep check strings concise, meanwhile recover the coverage of
case scev-8.c.

gcc/testsuite/ChangeLog

2020-03-02  Kewen Lin  <linkw@gcc.gnu.org>

  * gcc.dg/tree-ssa/scev-8.c: Revise check string.
  * gcc.dg/tree-ssa/scev-9.c: Ditto.
  * gcc.dg/tree-ssa/scev-10.c: Ditto.
  * gcc.dg/tree-ssa/scev-11.c: Ditto.
  * gcc.dg/tree-ssa/scev-12.c: Ditto.