sky2: don't look for VPD size

The code to compute VPD size didn't handle some systems that use
chip without VPD. Also some of the newer chips use some additional
registers to store the actual size, and wasn't worth putting the
additional complexity in, so just remove the code.

No big loss since the code to set the VPD size was only a
convenience so that utilities would not read the extra space past
the end of the available VPD.

Move the first PCI config read earlier to detect bad hardware
where it returns all ones and refuse loading driver before furthur
damage.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Tested-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>