Clean up save_failed_screen

include/save.h

@@ -29,6 +29,11 @@ struct SaveSectionOffsets
     u16 size;
 };
 
+// Each 4 KiB flash sector contains 3968 bytes of actual data followed by a 128 byte footer
+#define SECTOR_DATA_SIZE 3968
+#define SECTOR_FOOTER_SIZE 128
+#define SECTOR_SIZE (SECTOR_DATA_SIZE + SECTOR_FOOTER_SIZE)
+
 // Emerald changes this definition to be the sectors per slot.
 #define NUM_SECTORS_PER_SLOT 16