MIPS: DTS: CI20: fix otg power gpio

According to schematics it is PF15 and not PF14 (MIC_SW_EN).
Seems as if it was hidden and not noticed during testing since
there is no sound DT node.

Fixes: 158c774d ("MIPS: Ingenic: Add missing nodes for Ingenic SoCs and boards.")
Cc: stable@vger.kernel.org
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Acked-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>