MIPS: Loongson64: Drop legacy IRQ code

We've made generic irqchip drivers for Loongson-3 platform, it's time
to say goodbye to these legacy code.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Co-developed-by: Huacai Chen <chenhc@lemote.com>
Signed-off-by: Huacai Chen <chenhc@lemote.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
6 files changed