hw/riscv/virt.c: make aclint compatible with 'qtest' accel

hw/riscv/virt.c: make aclint compatible with 'qtest' accel

The 'virt' machine makes assumptions on the Advanced Core-Local
Interruptor, or aclint, based on 'tcg_enabled()' conditionals.  This
will impact MSI related tests support when adding a RISC-V 'virt' libqos
machine. The accelerator used in that case, 'qtest', isn't being
accounted for and we'll error out if we try to enable aclint.

Create a new virt_aclint_allowed() helper to gate the aclint code
considering both TCG and 'qtest' accelerators. The error message is
left untouched, mentioning TCG only, because we don't expect the
regular user to be aware of 'qtest'.

We want to add 'qtest' support for aclint only, leaving the TCG specific
bits out of it. This is done by changing the current format we use
today:

if (tcg_enabled()) {
   if (s->have_aclint) { - aclint logic - }
   else { - non-aclint, TCG logic - }
}

into:

if (virt_aclint_allowed() && s->have_aclint) {
 - aclint logic -
} else if (tcg_enabled()) {
 - non-aclint, TCG logic -
}

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20240217192607.32565-6-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>