Fix some Makefile comments

Marlin/Makefile

 # Ultimaker (Older electronics. Pre 1.5.4. This is rare)
 else ifeq ($(HARDWARE_MOTHERBOARD),71)
   MCU ?= atmega1280
+
 # Azteeg X3
 else ifeq ($(HARDWARE_MOTHERBOARD),67)
 # Azteeg X3 Pro
 	stty -hup < $(UPLOAD_PORT); true
 endif
 
-  # Display size of file.
+# Display size of file.
 HEXSIZE = $(SIZE) --target=$(FORMAT) $(BUILD_DIR)/$(TARGET).hex
 ELFSIZE = $(SIZE)  $(SIZE_FLAGS) $(BUILD_DIR)/$(TARGET).elf; \
           $(SIZE)  $(BUILD_DIR)/$(TARGET).elf
 .elf.sym:
 	$(NM) -n $< > $@
 
-  # Link: create ELF output file from library.
+# Link: create ELF output file from library.
 
 $(BUILD_DIR)/$(TARGET).elf: $(OBJ) Configuration.h
 	$(Pecho) "  CXX   $@"