sh-pfc: r8a7740: Replace GPIO_PORTx enum with GPIO port numbers

The PFC GPIO API implementation moved to using port numbers. Replace all
GPIO_PORTx enum usage with the corresponding port number. The GPIO_PORTx
enum values are identical to the port number on this platform.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>