Revert "iommu/io-pgtable-arm: Check for v7s-incapable systems"

This reverts commit 82db33dc.

After the commit 29859aeb

 ("iommu/io-pgtable-arm-v7s: Abort
allocation when table address overflows the PTE"), v7s will return fail
if the page table allocation isn't expected. this PHYS_OFFSET check
is unnecessary now.

And this check may lead to fail. For example, If CONFIG_RANDOMIZE_BASE
is enabled, the "memstart_addr" will be updated randomly, then the
PHYS_OFFSET may be random.

Reported-by: CK Hu <ck.hu@mediatek.com>
Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>