cxl: Read vsec perst load image

This bit is used to cause a flash image load for programmable
CAIA-compliant implementation. If this bit is set to ‘0’, a power
cycle of the adapter is required to load a programmable CAIA-com-
pliant implementation from flash.
This field will be used by the following patches.

Signed-off-by: Christophe Lombard <clombard@linux.vnet.ibm.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Acked-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>