sh-pfc: Don't modify pinmux_data_reg SoC data

The pinmux_data_reg structure supplied in SoC data contains information
about data registers. It's abused to store per-device mapped iomem and
shadow values. Move those fields out of the pinmux_data_reg structure
into the per-device sh_pfc_chip structure.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>