memory: Remove kernel-doc comment marker

memory: Remove kernel-doc comment marker

The IOMMUMemoryRegionClass struct documentation was never in the
kernel-doc format.  Stop pretending it is, by removing the "/**"
comment marker.

This fixes a documentation build error introduced when we split
the IOMMUMemoryRegionClass typedef from the struct declaration.

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200908173650.3293057-1-ehabkost@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>