virtio_pci_modern: correct sparse tags for notify

stable inclusion
from stable-v5.13
commit d7bce85a
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5WXCZ
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d7bce85aa7b92b5de8f69b3bcedfe51d7b1aabe1


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When switching virtio_pci_modern to use a helper for mappings we lost an
__iomem tag. Restore it.

Reported-by: kernel test robot <lkp@intel.com>
Fixes: 9e3bb9b7 ("virtio_pci_modern: introduce helper to map vq notify area")
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Pengyuan Zhao <zhaopengyuan@hisilicon.com>