tg3: improve PCI VPD access

tg3: improve PCI VPD access

When working on the PCI VPD code I also tested with a Broadcom BCM95719
card. tg3 uses internal NVRAM access with this card, so I forced it to
PCI VPD mode for testing. PCI VPD access fails
(i + PCI_VPD_LRDT_TAG_SIZE + j > len) because only TG3_NVM_VPD_LEN (256)
bytes are read, but PCI VPD has 400 bytes on this card.

So add a constant TG3_NVM_PCI_VPD_MAX_LEN that defines the maximum
PCI VPD size. The actual VPD size is returned by pci_read_vpd().
In addition it's not worth looping over pci_read_vpd(). If we miss the
125ms timeout per VPD dword read then definitely something is wrong,
and if the tg3 module loading is killed then there's also not much
benefit in retrying the VPD read.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Link: https://lore.kernel.org/r/cb9e9113-0861-3904-87e0-d4c4ab3c8860@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>