Add MacAddress string constructor (#9400)

* Add MacAddress string constructor

* Change implementation

cores/esp32/MacAddress.cpp

@@ -28,6 +28,10 @@ MacAddress::MacAddress(const char *macstr){
     fromString(macstr);
 }
 
+MacAddress::MacAddress(const String &macstr){
+    fromString(macstr.c_str());
+}
+
 MacAddress::MacAddress(uint8_t b1, uint8_t b2, uint8_t b3, uint8_t b4, uint8_t b5, uint8_t b6) {
     _type = MAC6;
     memset(_mac.bytes, 0, sizeof(_mac.bytes));

cores/esp32/MacAddress.h

@@ -54,6 +54,7 @@ public:
     MacAddress(const uint8_t *macbytearray) : MacAddress(MAC6, macbytearray) {}
 
     MacAddress(const char *macstr);
+    MacAddress(const String &macstr);
 
     virtual ~MacAddress() {}