hw/nios2: Machine with a Vectored Interrupt Controller

hw/nios2: Machine with a Vectored Interrupt Controller

Demonstrate how to use nios2 VIC on a machine.
Introduce a new machine property to attach a VIC.

When VIC is present, let the CPU know that it should use the
External Interrupt Interface instead of the Internal Interrupt Interface.
The devices on the machine are attached to the VIC and not directly to cpu.
To allow VIC update EIC fields, we set the "cpu" property of the VIC
with a reference to the nios2 cpu.

[rth: Put a property on the 10m50-ghrd machine, rather than
      create a new machine class.]

Reviewed-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: Amir Gonnen <amir.gonnen@neuroblade.ai>
Message-Id: <20220303153906.2024748-6-amir.gonnen@neuroblade.ai>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220421151735.31996-63-richard.henderson@linaro.org>