vfio-pci: Use io_remap_pfn_range() for PCI IO memory

stable inclusion
from linux-4.19.164
commit bb3130192ff9333f93ca02cb6f17144cf55ba4d8

--------------------------------

[ Upstream commit 7b06a56d ]

commit f8f6ae5d ("mm: always have io_remap_pfn_range() set
pgprot_decrypted()") allows drivers using mmap to put PCI memory mapped
BAR space into userspace to work correctly on AMD SME systems that default
to all memory encrypted.

Since vfio_pci_mmap_fault() is working with PCI memory mapped BAR space it
should be calling io_remap_pfn_range() otherwise it will not work on SME
systems.

Fixes: 11c4cd07 ("vfio-pci: Fault mmaps to enable vma tracking")
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Peter Xu <peterx@redhat.com>
Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>