ospfd: compile warning cleanups

A set of patches to clarify some comments as well as cleanup code that was
causing warnings.  After these patches, the code can be compiled with

-Wall -Wsign-compare -Wpointer-arith -Wbad-function-cast -Wwrite-strings
-Wmissing-prototypes -Wmissing-declarations -Wchar-subscripts -Wcast-qual
-Wextra -Wno-unused-parameter -Wno-missing-field-initializers

(what is current in trunk plus -Wextra -Wno-unused-parameter
-Wno-missing-field-initializers).

Signed-off-by: Scott Feldman <sfeldma@cumulusnetworks.com>
diff --git a/ospfd/ospf_lsa.c b/ospfd/ospf_lsa.c
index fb55f7f..4f7fb00 100644
--- a/ospfd/ospf_lsa.c
+++ b/ospfd/ospf_lsa.c
@@ -2733,7 +2733,9 @@
       if (IS_LSA_SELF (lsa))
 	lsa->oi = oi; /* Specify outgoing ospf-interface for this LSA. */
       else
-	; /* Incoming "oi" for this LSA has set at LSUpd reception. */
+        {
+          /* Incoming "oi" for this LSA has set at LSUpd reception. */
+        }
       /* Fallthrough */
     case OSPF_OPAQUE_AREA_LSA:
     case OSPF_OPAQUE_AS_LSA: