It is not an Easter egg, I can assure you. There is actually a shrine near Kyoto-the location of Nintendo's headquarters-boasting the same symbol. It' pretty common actually and as Zelda fans we commonly refer to it as the "Triforce". The symbol has a lot of bckstory in Japan. It was first a symbol of the Hojo family and is now used as the emblem for the energy corporation Mitsuuroko. In the Western world, the symbol carries less significance but is associated with the 13th century Sierpinksi Triangle and was actually used as a symbol for the Ku Klux Klan. Nintendo essentially "borrowed" the entire "Triforce"and put it in Zelda. The emblem's history as I detailed above is much deeper. I suggest you read more on the topic
here.