target/arm: Enable FEAT_Debugv8p4 for -cpu max

target/arm: Enable FEAT_Debugv8p4 for -cpu max

This extension concerns changes to the External Debug interface,
with Secure and Non-secure access to the debug registers, and all
of it is outside the scope of QEMU.  Indicating support for this
is mandatory with FEAT_SEL2, which we do implement.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220506180242.216785-13-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>