Having a function return either and valid TB and some system state
seems excessive. It will make the subsequent re-factoring easier if we
lookup the current state where we are.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20210224165811.11567-2-alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>