system/cpu-timers: Have icount_configure() return a boolean

system/cpu-timers: Have icount_configure() return a boolean

Following the example documented since commit e3fe3988d7 ("error:
Document Error API usage rules"), have icount_configure()
return a boolean indicating whether an error is set or not.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20231208113529.74067-2-philmd@linaro.org>