cxlflash: Use new cxl_pci_read_adapter_vpd() API

cxlflash: Use new cxl_pci_read_adapter_vpd() API

BugLink: http://bugs.launchpad.net/bugs/1588468
To read the adapter VPD, drivers can't rely on pci config APIs, as it
wouldn't work on powerVM. cxl introduced a new kernel API especially
for this, so start using it.

Co-authored-by: Christophe Lombard <clombard@linux.vnet.ibm.com>
Signed-off-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Christophe Lombard <clombard@linux.vnet.ibm.com>
Reviewed-by: Uma Krishnan <ukrishn@linux.vnet.ibm.com>
Acked-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Acked-by: Manoj N. Kumar <manoj@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
(cherry picked from commit ca946d4e4a390a5121bfc9076d85be0ddd55c266)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>