This makes SMP on the vrx200 work again, by removing all the MIPS CPU
interrupt specific code and making it fully use the generic MIPS CPU
interrupt controller.

The mti,cpu-interrupt-controller from irq-mips-cpu.c now handles the CPU
interrupts and also the IPI interrupts which are used to communication
between the CPUs in a SMP system. The generic interrupt code was
already used before but the interrupt vectors were overwritten again
when we called set_vi_handler() in the lantiq interrupt driver and we
also provided our own plat_irq_dispatch() function which overwrote the
weak generic implementation. Now the code uses the generic handler for
the MIPS CPU interrupts including the IPI interrupts and registers a
handler for the CPU interrupts which are handled by the lantiq ICU with
irq_set_chained_handler() which was already called before.

Calling the set_c0_status() function is also not needed any more because
the generic MIPS CPU interrupt already activates the needed bits.

Fixes: 1eed4004 ("MIPS: smp-mt: Use CPU interrupt controller IPI IRQ domain support")
Cc: stable@kernel.org # v4.12
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: jhogan@kernel.org
Cc: ralf@linux-mips.org
Cc: john@phrozen.org
Cc: linux-mips@linux-mips.org
Cc: linux-mips@vger.kernel.org