PCI: set pci sriov page size before reading SRIOV BAR

For an SRIOV device, PCI_SRIOV_SYS_PGSIZE should be set before
the PCI_SRIOV_BAR are queried.  The sys pagesize defaults to 4k,
so this change is required on powerpc box with 64k base page size.
    
This is a regression caused due to moving SRIOV init to sriov_enable().
    
| commit afd24ece
| Author: Ram Pai <linuxram@us.ibm.com>
    
| 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.
    
Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Acked-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>