vfio-pci: Handle error from pci_iomap

vfio-pci: Handle error from pci_iomap

BugLink: http://bugs.launchpad.net/bugs/1710646
[ Upstream commit e19f32da5ded958238eac1bbe001192acef191a2 ]

Here, pci_iomap can fail, handle this case release selected
pci regions and return -ENOMEM.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>