target/arm/kvm: gic: Prevent creating userspace GICv3 with KVM

target/arm/kvm: gic: Prevent creating userspace GICv3 with KVM

KVM doesn't support emulating a GICv3 in userspace, only GICv2.  We
currently attempt this anyway, and as a result a KVM guest doesn't
receive interrupts and the user is left wondering why.  Report an error
to the user if this particular combination is requested.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20180201205307.30343-1-christoffer.dall@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>