Use Doxygen style comments consistently.

We were already using them for functions; use them for struct members
and enum values as well.

Change-Id: I89c1ef9e4a4f19424186b4da5855522bac0a2c4d
diff --git a/inc/hf/addr.h b/inc/hf/addr.h
index 7121744..09a6c09 100644
--- a/inc/hf/addr.h
+++ b/inc/hf/addr.h
@@ -21,17 +21,17 @@
 
 #include "hf/arch/addr.h"
 
-/* An opaque type for a physical address. */
+/** An opaque type for a physical address. */
 typedef struct {
 	uintpaddr_t pa;
 } paddr_t;
 
-/* An opaque type for an intermediate physical address. */
+/** An opaque type for an intermediate physical address. */
 typedef struct {
 	uintpaddr_t ipa;
 } ipaddr_t;
 
-/* An opaque type for a virtual address. */
+/** An opaque type for a virtual address. */
 typedef struct {
 	uintvaddr_t va;
 } vaddr_t;