pinctrl: sh-pfc: r8a7778: Use common PORT_GP_CFG_27() macro

Get rid of the custom PORT_GP_PUP_27() macro by using the common
PORT_GP_CFG_27() macro instead.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>