machine: Use error handling when CPU type is checked

machine: Use error handling when CPU type is checked

Functions that use an Error **errp parameter to return errors should
not also report them to the user, because reporting is the caller's
job. The principle is violated by machine_run_board_init() because
it calls error_report(), error_printf(), and exit(1) when the machine
doesn't support the requested CPU type.

Clean this up by using error_setg() and error_append_hint() instead.
No functional change, as the only caller passes &error_fatal.

Suggested-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20231204004726.483558-2-gshan@redhat.com>
[PMD: Correct error_append_hint() argument]
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>