Input: sh_keysc - restrict non-COMPILE_TEST compilation

Hardware supported by the driver is only found on SUPERH or
ARCH_SHMOBILE platforms. Restrict non-COMPILE_TEST compilation to them.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>