hw/intc/arm_gicv3: Allow 'revision' property to be set to 4

hw/intc/arm_gicv3: Allow 'revision' property to be set to 4

Now that we have implemented all the GICv4 requirements, relax the
error-checking on the GIC object's 'revision' property to allow a TCG
GIC to be a GICv4, whilst still constraining the KVM GIC to GICv3.

Our 'revision' property doesn't consider the possibility of wanting
to specify the minor version of the GIC -- for instance there is a
GICv3.1 which adds support for extended SPI and PPI ranges, among
other things, and also GICv4.1.  But since the QOM property is
internal to QEMU, not user-facing, we can cross that bridge when we
come to it. Within the GIC implementation itself code generally
checks against the appropriate ID register feature bits, and the
only use of s->revision is for setting those ID register bits.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220408141550.1271295-39-peter.maydell@linaro.org