sh-pfc: r8a7778: add common PFC macro helper

pfc-r8a7778 will have many devices pfc support in the future,
and current pfc-r8a7778 is using pin/mux definition macro for SCIF.
The device definition style using macro is readable code IMO,
but creating new macro for each devices is not good sense.
This patch adds common SH_PFC_xx() macro for each new feature devices

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>