PCI-2.2 VPD entries have a maximum size of 32k, but might actually be
smaller than that.  To figure out the actual size one has to read the VPD
area until the 'end marker' is reached.

Per spec, reading outside of the VPD space is "not allowed."  In practice,
it may cause simple read errors or even crash the card.  To make matters
worse not every PCI card implements this properly, leaving us with no 'end'
marker or even completely invalid data.

Try to determine the size of the VPD data when it's first accessed.  If no
valid data can be read an I/O error will be returned when reading or
writing the sysfs attribute.

As the amount of VPD data is unknown initially the size of the sysfs
attribute will always be set to '0'.

[bhelgaas: changelog, use 0/1 (not false/true) for bitfield, tweak
pci_vpd_pci22_read() error checking]
Tested-by: Shane Seymour <shane.seymour@hpe.com>
Tested-by: Babu Moger <babu.moger@oracle.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Alexander Duyck <alexander.duyck@gmail.com>