hw/cxl/cxl-cdat: Make cxl_doe_cdat_init() return boolean

hw/cxl/cxl-cdat: Make cxl_doe_cdat_init() return boolean

As error.h suggested, the best practice for callee is to return
something to indicate success / failure.

With returned boolean, there's no need to dereference @errp to check
failure case.

Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-ID: <20240418100433.1085447-4-zhao1.liu@linux.intel.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>