pinctrl: sh-pfc: IPSRx and MOD_SELx should be set before GPSRx

Gen2 / Gen3 datasheet will have below note in next version.
This patch follows this note.

IPSRx and MOD_SELx registers shall be set before setting GPSRx
registers in case that they need to be configured.
MOD_SELx registers can be set either earlier or later than setting
IPSRx registers.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>