s390/vmem: fix empty page tables cleanup under KASAN

s390/vmem: fix empty page tables cleanup under KASAN

[ Upstream commit 7eb8eb333f4131c53b2ca07a0d17a6d736462b5c ]

Commit 2245fe9cff28 ("s390/vmem: cleanup empty page tables") introduced
empty page tables cleanup in vmem code, but when the kernel is built
with KASAN enabled the code has no effect due to wrong KASAN shadow
memory intersection condition, which effectively ignores any memory
range below KASAN shadow. Fix intersection condition to make code
work as anticipated.

Fixes: 2245fe9cff28 ("s390/vmem: cleanup empty page tables")
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>