If you've beaten the game, you would know that Ghirahim is actually the evil counterpart to Fi. Ghirahim is transformed into Demise's sword, which the latter uses in the final battle. Noting how Fi's character design doesn't boast the pointed ears as do the Hylians, the one non-pointed ear I'd assume is to symbolize that Ghirahim is not a Hylian like Link or Zelda. When Ghirahim is transformed to his final form, the two pointed ears is likely to symbolize his true nature as being able to think for himself and as an individual with thought. His hairstyle, however, is very close to that of Fi's, keeping it in line with the design of him actually being the counterpart to her.