server3: Create PCIe Bifurcation for server3.0

Add Server3PcieBifurcation to handle the logic for server3.0 platforms. This commit don't change server2's logic since it uses a macro to decide which class to use.

Tested:
root@server3:~# hexdump -C /mnt/luks-mmcblk0_fs/bios/image-bios-0 | head
00000000  06 01 08 00 03 08 08 08  00 00 00 ff ff ff ff ff  |................|
00000010  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
root@server3:~# hexdump -C /mnt/luks-mmcblk0_fs/bios/image-bios-1 | head
00000000  06 01 08 00 03 08 08 08  00 00 00 ff ff ff ff ff  |................|
00000010  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|

Google-Bug-Id: 452190090
Change-Id: I80f435363f58e62519e0624e354473ecf877159e
Signed-off-by: Anh Phan <anhphan@google.com>