pinctrl: sh-pfc: r8a7791: Grand I2C rename

The R8A7791 PFC driver was apparently based on the preliminary revisions
of the user's manual, which called all the I2C signals {SCL|SDA}<n> and
MOD_SEL register fields SEL_IIC<n> without making a difference between
two types of the I2C controllers used.  The recent manual calls the
signals {I2C|IIC}<n>_{SCL|SDA> and the MOD_SEL fields SEL_{I2C|IIC}<n>
finally making this difference.  Follow the suit...

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>