PCI: rockchip: Set vendor ID from local core config space

The TRM says the vendor ID in the RC's configure space can be rewritten
and the value must be the same as the value read from the local core
configure space.  But we misread that and didn't notice it before.  Actually
we should only able to rewrite it from the local core configure space.

Fix that issue to make lspci show the correct IP vendor infomation.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>