MIPS: Loongson 3: Add HT-linked PCI support

MIPS: Loongson 3: Add HT-linked PCI support

Loongson family machines use Hyper-Transport bus for inter-core
connection and device connection. The PCI bus is a subordinate
linked at HT1.

With LEFI firmware interface, We don't need fixup for PCI irq routing
(except providing a VBIOS of the integrated GPU).

Signed-off-by: Huacai Chen <[email protected]>
Signed-off-by: Hongliang Tao <[email protected]>
Signed-off-by: Hua Yan <[email protected]>
Tested-by: Alex Smith <[email protected]>
Reviewed-by: Alex Smith <[email protected]>
Cc: John Crispin <[email protected]>
Cc: Steven J. Hill <[email protected]>
Cc: Aurelien Jarno <[email protected]>
Cc: [email protected]
Cc: Fuxin Zhang <[email protected]>
Cc: Zhangjin Wu <[email protected]>
Patchwork: https://patchwork.linux-mips.org/patch/6633
Signed-off-by: Ralf Baechle <[email protected]>