src/device/pci: Add support for discrete VGA initialization and OpROM loading

Required to make the discrete VGA working at boards like Lenovo G505S
where the discrete VGA doesn't have its own memory for storing a VBIOS.

If CONFIG_MULTIPLE_VGA_ADAPTERS is enabled: coreboot will try to
initialize the discrete VGA of PCI_CLASS_DISPLAY_OTHER class and
load VBIOS OpROM on it. ACPI VFCT table will be created only for
discrete VGA of PCI_CLASS_DISPLAY_OTHER class instead of integrated
(to avoid the discrete VGA init problems), but everything is working
fine. Later will try to make a common VFCT table for both adapters.

Based on the original patches by Hans Jürgen Kitter <eforname@freemail.hu>.

Signed-off-by: Mike Banon <mikebdp2@gmail.com>
Change-Id: I9a7aa31c956d8f716e2d5a73ff032134c144d3db
---
M src/device/pci_device.c
M src/device/pci_rom.c
2 files changed, 74 insertions(+), 11 deletions(-)