Interface to mark SR-IOV device ready for use by LDoms guest

Interface to mark SR-IOV device ready for use by LDoms guest

Add a iov_ready file to all PCI devices (/sys/bus/pci/devices/*/iov_ready).
The iov_ready file is write only, and mapped to the pci_iov_dev_ready
hypervisor call, which is used to indicate that a PCI device is ready
or no longer ready to be shared with other domains

Write "1" to the file to indicate that the PCI device is ready.
For example:

  # echo 1 > /sys/bus/pci/devices/0001:03:00.0/iov_ready

Write "0" to the file to indicate that the PCI device is no longer ready.
For example:

  # echo 0 > /sys/bus/pci/devices/0001:03:00.0/iov_ready

Orabug: 22909608

Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Babu Moger <babu.moger@oracle.com>
Signed-off-by: Allen Pais <allen.pais@oracle.com>
(cherry picked from commit 14f6e82264924f1db2cad628edae7964caa9c03e)