memory: introduce memory_region_present

This new API will avoid having too many memory_region_ref/unref
in paths that currently use memory_region_find.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/include/exec/memory.h b/include/exec/memory.h
index d2466a7..c8d0bf4 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -837,6 +837,18 @@
                                     hwaddr offset);
 
 /**
+ * memory_region_present: translate an address/size relative to a
+ * MemoryRegion into a #MemoryRegionSection.
+ *
+ * Answer whether a #MemoryRegion within @parent covers the address
+ * @addr.
+ *
+ * @parent: a MemoryRegion within which @addr is a relative address
+ * @addr: the area within @parent to be searched
+ */
+bool memory_region_present(MemoryRegion *parent, hwaddr addr);
+
+/**
  * memory_region_find: translate an address/size relative to a
  * MemoryRegion into a #MemoryRegionSection.
  *