fix RAMSTART, RAMSIZE, RAMEND for samd51 and same21

Author: hathach

cores/arduino/avr/io.h

@@ -25,8 +25,14 @@
 #ifndef _IO_H_
 #define _IO_H_
 
-#define RAMSTART (HMCRAMC0_ADDR)
-#define RAMSIZE  (HMCRAMC0_SIZE)
+#ifdef HSRAM_ADDR
+  #define RAMSTART (HSRAM_ADDR)
+  #define RAMSIZE  (HSRAM_SIZE)
+#else
+  #define RAMSTART (HMCRAMC0_ADDR)
+  #define RAMSIZE  (HMCRAMC0_SIZE)
+#endif
+
 #define RAMEND   (RAMSTART + RAMSIZE - 1)
 
 #endif