target/arm: Wrap breakpoint/watchpoint updates with tcg_enabled This is in preparation for restricting compilation of some parts of debug_helper.c to TCG only. Signed-off-by: Fabiano Rosas <farosas@suse.de> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>