MIPS: Loongson64: Switch to generic PCI driver

We can now enable generic PCI driver in Kconfig, and remove legacy
PCI driver code.

Radeon vbios quirk is moved to the platform folder to fit the
new structure.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>