target/alpha: Use cpu_env in preference to ALPHA_CPU

ALPHA_CPU has a dynamic object type assert, which is
unnecessary considering that these are all class hooks.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20240503072014.24751-2-philmd@linaro.org>
2 files changed