pinctrl: sh-pfc: r8a7794: Rename some I2C signals

The R8A7794 PFC driver was apparently based on the preliminary revisions
of the user's manual which called I2C5 device IIC0 and IIC0 device IIC1.
Luckily, these signals haven't been used for any functions/groups so
far, so the renaming should be painless..
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>