hw/intc/riscv_aplic: add kvm_msicfgaddr for split mode aplic-imsic

hw/intc/riscv_aplic: add kvm_msicfgaddr for split mode aplic-imsic

The last step to enable KVM AIA aplic-imsic with irqchip in split mode
is to deal with how MSIs are going to be sent. In our current design we
don't allow an APLIC controller to send MSIs unless it's on m-mode. And
we also do not allow Supervisor MSI address configuration via the
'smsiaddrcfg' and 'smsiaddrcfgh' registers unless it's also a m-mode
APLIC controller.

Add a new RISCVACPLICState attribute called 'kvm_msicfgaddr'. This
attribute represents the base configuration address for MSIs, in our
case the base addr of the IMSIC controller. This attribute is being set
only when running irqchip_split() mode with aia=aplic-imsic.

During riscv_aplic_msi_send() we'll check if the attribute was set to
skip the check for a m-mode APLIC controller and to change the resulting
MSI addr by adding kvm_msicfgaddr right before address_space_stl_le().

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20241119191706.718860-7-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>