Correct AVR_ATmega328_FAMILY macro

…as with #10540

Co-Authored-By: per1234 <per1234@users.noreply.github.com>

Marlin/src/HAL/HAL_AVR/fastio_AVR.h

@@ -36,7 +36,7 @@
 #define AVR_ATmega1284_FAMILY (defined(__AVR_ATmega644__) || defined(__AVR_ATmega644P__) || defined(__AVR_ATmega644PA__) || defined(__AVR_ATmega1284P__))
 #define AVR_ATmega2560_FAMILY (defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__))
 #define AVR_ATmega2561_FAMILY (defined(__AVR_ATmega1281__) || defined(__AVR_ATmega2561__))
-#define AVR_ATmega328_FAMILY (defined(__AVR_ATmega168__) || defined(__AVR_ATmega328__) || defined(__AVR_ATmega328p__))
+#define AVR_ATmega328_FAMILY (defined(__AVR_ATmega168__) || defined(__AVR_ATmega328__) || defined(__AVR_ATmega328P__))
 
 /**
  * Include Ports and Functions