PCI: aardvark: Implement workaround for the readback value of VEND_ID

PCI: aardvark: Implement workaround for the readback value of VEND_ID

Marvell Armada 3700 Functional Errata, Guidelines, and Restrictions
document describes in erratum 4.1 PCIe value of vendor ID (Ref #: 243):

    The readback value of VEND_ID (RD0070000h [15:0]) is 1B4Bh, while it
    should read 11ABh.

    The firmware can write the correct value, 11ABh, through VEND_ID
    (RD0076044h [15:0]).

Implement this workaround in aardvark driver for both PCI vendor id and PCI
subsystem vendor id.

This change affects and fixes PCI vendor id of emulated PCIe root bridge.
After this change emulated PCIe root bridge has correct vendor id.

Link: https://lore.kernel.org/r/20210624222621.4776-5-pali@kernel.org
Fixes: 56faa9cfa347 ("PCI: aardvark: Implement emulated root PCI bridge config space")
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Marek Behún <kabel@kernel.org>
Cc: stable@vger.kernel.org