MIPS: lantiq: Add SMP support for lantiq interrupt controller

Some lantiq devices have two ICU controllers. The IRQ signal is routed
to both of them and user can chose which ICU will resend the IRQ to their
respective VPE. The patch adds the support for the second ICU.

The patch changes a register definition of the driver. Instead of an
individual IM, the whole ICU is defined. This will only affects openwrt
patched kernel (vanilla doesn't have additional .dts files).

Also spinlocks has been added, both cores can RMW different bitfields
in the same register. Added affinity set function. The new VPE cpumask
will take into the action at the irq enable.

The functionality was tested on 4.14 openwrt kernel and TP-W9980B modem.

Signed-off-by: Petr Cvek <petrcvekcz@gmail.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: hauke@hauke-m.de
Cc: john@phrozen.org
Cc: linux-mips@vger.kernel.org
Cc: openwrt-devel@lists.openwrt.org
Cc: pakahmar@hotmail.com