hw/core: fix whitespace in a sentence

Signed-off-by: NWainer dos Santos Moschetta <wainersm@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20181224154922.3338-1-wainersm@redhat.com>
Signed-off-by: NLaurent Vivier <laurent@vivier.eu>