The watchpoint API is specific to TCG system emulation.

Move it to a new compile unit. The inlined stubs are used
for user-mode and non-TCG accelerators.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20221209141254.68662-1-philmd@linaro.org>