[meshcop] reduce maximum number types in MGMT_GET.req (#4740)

src/core/meshcop/dataset.hpp

@@ -56,6 +56,7 @@ public:
     {
         kMaxSize      = 256, ///< Maximum size of MeshCoP Dataset (bytes)
         kMaxValueSize = 16,  ///< Maximum size of each Dataset TLV value (bytes)
+        kMaxGetTypes  = 64,  ///< Maximum number of types in MGMT_GET.req
     };
 
     /**

src/core/meshcop/dataset_manager.cpp

@@ -299,7 +299,7 @@ void DatasetManager::HandleGet(const Coap::Message &aMessage, const Ip6::Message
 {
     Tlv      tlv;
     uint16_t offset = aMessage.GetOffset();
-    uint8_t  tlvs[Dataset::kMaxSize];
+    uint8_t  tlvs[Dataset::kMaxGetTypes];
     uint8_t  length = 0;
 
     while (offset < aMessage.GetLength())