in the asm file, change to this, compile, upload and Bob's your uncle:
;; number of LCD lines (supported: 2 for 2x* LCDs and 4 for 4x* LCDs)
#define DEFAULT_LCD_LINES 4
;; LCD line -> cursor offsets
#define DEFAULT_LCD_LINE_Y0 0x40
#define DEFAULT_LCD_LINE_Y1 0x14
#define DEFAULT_LCD_LINE_Y2 0x00
#define DEFAULT_LCD_LINE_Y3 0x54