ARM: shmobile: alt: Add pfc pins to DT

PFC is already enabled on the r8a7794.
This adds pins for devices already enabled in DT on
the r8a7794 based alt board.

Based on work by Mitsuhiro Kimura and Hisashi Nakamura.

Cc: Mitsuhiro Kimura <mitsuhiro.kimura.kc@renesas.com>
Cc: Hisashi Nakamura <hisashi.nakamura.ak@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>