accel/tcg: Move common declarations to 'internal-common.h'

'internal-target.h' is meant for target-specific declarations,
while 'internal-common.h' for common ones. Move common declarations
to it.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Message-Id: <20240528145953.65398-3-philmd@linaro.org>