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>
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 0cfe987..90e2470 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -216,7 +216,7 @@
     IOMMU_ATTR_SPAPR_TCE_FD
 };
 
-/**
+/*
  * IOMMUMemoryRegionClass:
  *
  * All IOMMU implementations need to subclass TYPE_IOMMU_MEMORY_REGION