sra: Fix the fix for PR 102505 (PR 102886)

sra: Fix the fix for PR 102505 (PR 102886)

I was not careful with the fix for PR 102505 and did not craft the
check to satisfy the verifier carefully, which lead to PR 102886.
(The verifier has the test structured differently and somewhat
redundantly, so I could not just copy it).

This patch fixes it.  I hope it is quite obvious correction of an
oversight and so will commit it if survives bootstrap and testing on
x86_64-linux and ppc64le-linux.

Testcase for this bug is gcc.dg/tree-ssa/sra-18.c (but only on
platforms with constant pools).  I will backport the two fixes
to the release branches squashed.

gcc/ChangeLog:

2021-10-22  Martin Jambor  <mjambor@suse.cz>

	PR tree-optimization/102886
	* tree-sra.c (totally_scalarize_subtree): Fix the out of
	access-condition.