ARM: shmobile: r8a7779: Use macros to declare SCIF devices

Replace copy-n-paste SCIF platform data and device declaration with a
macro. This reduces the amount of code and improves readability.

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