target/arm: Move some register related defines to internals.h

target/arm: Move some register related defines to internals.h

cpu.h has a lot of #defines relating to CPU register fields.
Most of these aren't actually used outside target/arm code,
so there's no point in cluttering up the cpu.h file with them.
Move some easy ones to internals.h.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20240301183219.2424889-2-peter.maydell@linaro.org