testsuite: Fix up pr64536.c for LLP64 targets [PR108151]

testsuite: Fix up pr64536.c for LLP64 targets [PR108151]

The test casts a pointer to long, which is ok for ilp32 and lp64
targets but not for llp64 targets.  Nothing reads the values later,
it is a link test, so all we care about is that it is the same
cast on s390x-linux where it used to fail before the PR64536 fix,
and that we don't warn about it.

2022-12-19  Jakub Jelinek  <jakub@redhat.com>

	PR testsuite/108151
	* gcc.dg/pr64536.c (bar): Use casts to __INTPTR_TYPE__ rather than
	long when casting pointer to integral type.