IGD is PCIe device and has extended configuration space. Checking
the binary dump, we can see we have Caps located out of PCI compatible
Configuration Space range.

0x000: 86 80 12 19 17 04 10 00 06 00 00 03 00 00 00 00
0x010: 04 00 00 10 08 00 00 00 0c 00 00 00 08 00 00 00
0x020: 00 00 00 00 00 00 00 00 00 00 00 00 28 10 b9 06
0x030: 00 f8 ff ff 40 00 00 00 00 00 00 00 0b 01 00 00
0x040: 09 70 0c 01 71 26 01 62 c8 00 04 84 00 00 00 00
0x050: c1 00 00 00 39 00 00 00 00 00 00 00 01 00 00 a2
0x060: 00 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00
0x070: 10 ac 92 00 00 80 00 10 00 00 00 00 00 00 00 00
0x080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x090: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0a0: 00 00 00 00 00 00 00 00 00 00 00 00 05 d0 01 00
0x0b0: 18 00 e0 fe 00 00 00 00 00 00 00 00 00 00 00 00
0x0c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0d0: 01 00 22 00 00 80 00 00 00 00 00 00 00 00 00 00
0x0e0: 00 00 00 00 00 00 00 00 00 80 00 00 00 00 00 00
0x0f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x100: 1b 00 01 20 02 14 00 00 00 00 00 00 00 00 00 00
...

Currently, we only emulate the PCI compatible Configuration Space.
This is okay if we attach vGPU to PCI bus. But when we attach to
a PCI Express bus (when Qemu emulates a Intel Q35 chipset which has
PCIe slot), it will not work. Extended Configuration Space is required
for a PCIe device.

This patch extended the virtual configuration space from 256 bytes
to 4KB bytes. So we are to be a *real* PCIe device. And for the
Extended CapList we keep same to physical GPU.

Cc: Laszlo Ersek <lersek@redhat.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Changbin Du <changbin.du@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>