PCI: delay configuration of SRIOV capability

The SRIOV capability, namely page size and total_vfs of a device are
configured during enumeration phase of the device.  This can potentially
interfere with the PCI operations of the platform, if the IOV capability
of the device is not enabled.

The following patch postpones the configuration of the IOV capability of
the device to a later point, when the IOV capability is explicitly
enabled by the device driver.

The patch is tested on x86 and power platform.

Tested-by: Donald Dutile <ddutile@redhat.com>
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>