Use MaxLockMode symbol in more places.

As long as we have this macro, it makes sense to use it in
the LockMethodData structures.

Julien Rouhaud

Discussion: https://postgr.es/m/20220103064722.ewdv4evlez5m7mdn@jrouhaud

src/backend/storage/lmgr/lock.c

@@ -124,7 +124,7 @@ static bool Dummy_trace = false;
 #endif
 
 static const LockMethodData default_lockmethod = {
-	AccessExclusiveLock,		/* highest valid lock mode number */
+	MaxLockMode,
 	LockConflicts,
 	lock_mode_names,
 #ifdef LOCK_DEBUG
@@ -135,7 +135,7 @@ static const LockMethodData default_lockmethod = {
 };
 
 static const LockMethodData user_lockmethod = {
-	AccessExclusiveLock,		/* highest valid lock mode number */
+	MaxLockMode,
 	LockConflicts,
 	lock_mode_names,
 #ifdef LOCK_DEBUG

src/include/storage/lockdefs.h

@@ -45,7 +45,7 @@ typedef int LOCKMODE;
 #define AccessExclusiveLock		8	/* ALTER TABLE, DROP TABLE, VACUUM FULL,
 									 * and unqualified LOCK TABLE */
 
-#define MaxLockMode				8
+#define MaxLockMode				8	/* highest standard lock mode */
 
 
 /* WAL representation of an AccessExclusiveLock on a table */