sh-pfc: r8a7778: tidyup MMC_D1 pin

MMC_D1 is RCAR_GP_PIN(1, 8), not RCAR_GP_PIN(2, 8)

Reported-by: Yusuke Goda <yusuke.goda.sx@renesas.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>