[network-data] changing kMaxServerDataSize and kMaxServiceDataSize to #defines (#2408)

The size of the server and service data is not really an enum.
Additionally the formatting of the enum was different from the other enums.

include/openthread/types.h

@@ -812,18 +812,8 @@ typedef enum otRoutePreference
     OT_ROUTE_PREFERENCE_HIGH = 1,   ///< High route preference.
 } otRoutePreference;
 
-enum
-{
-    /**
-     * Maximum size of Service Data in bytes.
-     */
-    kMaxServiceDataSize = 252,
-
-    /**
-     * Maximum size of Server Data in bytes. This is theoretical limit, practical one is much lower.
-     */
-    kMaxServerDataSize = 248,
-};
+#define OT_SERVICE_DATA_MAX_SIZE 252    ///< Maximum size of Service Data in bytes.
+#define OT_SERVER_DATA_MAX_SIZE  248    ///< Maximum size of Server Data in bytes. This is theoretical limit, practical one is much lower.
 
 /**
  * This structure represents a Server configuration.
@@ -843,7 +833,7 @@ typedef struct otServerConfig
     /**
      * Server data bytes
      */
-    uint8_t mServerData[kMaxServerDataSize];
+    uint8_t mServerData[OT_SERVER_DATA_MAX_SIZE];
 
     /**
      * The Server Rloc.
@@ -874,7 +864,7 @@ typedef struct otServiceConfig
     /**
      * Service data bytes
      */
-    uint8_t mServiceData[kMaxServiceDataSize];
+    uint8_t mServiceData[OT_SERVICE_DATA_MAX_SIZE];
 
     /**
      * The Server configuration.