bridge: fix STP roles and protos strings

Add the missing commas that got lost in e5539fb618.

PR:		252532
Reviewd by:	kp@, donner@, freqlabs@
MFC after:	3 days
Differential Revision:	https://reviews.freebsd.org/D28425

sys/net/if_bridgevar.h

@@ -278,15 +278,15 @@ struct ifbpstpconf {
     "discarding"
 
 #define STP_PROTOS \
-    "stp"          \
-    "-"            \
+    "stp",         \
+    "-",           \
     "rstp"
 
 #define STP_ROLES \
-    "disabled"    \
-    "root"        \
-    "designated"  \
-    "alternate"   \
+    "disabled",   \
+    "root",       \
+    "designated", \
+    "alternate",  \
     "backup"
 
 #define PV2ID(pv, epri, eaddr)	do { \