Get Spritesheet Graphic Height

#   ROUTINE: GET SPRITESHEET GRAPHIC HEIGHT
#       Gets spritesheet graphic height.
#       Parameters:
#           r4 = (spritesheetID) Spritesheet ID
#       Returns:
#           r2 = Graphic height of spritesheet with specified ID

80081af0: 3084ffff andi r4,r4,0xffff                #   spritesheetID
80081af4: 00042080 sll r4,r4,0x02                   #   spritesheetID * 4
80081af8: 3c018009 lui r1,0x8009
80081afc: 00240821 addu r1,r1,r4
80081b00: 9022474a lbu r2,0x474a(r1)                #   return spritesheetData[spritesheetID].graphicHeight;
80081b04: 03e00008 jr r31
80081b08: 00000000 nop