ARM: shmobile: r8a7790: switch console back to scif0

The boot loader uses scif0, and so must we if we want earlycon to work.

Partially reverts 7c055894 ("ARM: shmobile: r8a7790: switch from scif
to scifa").

Signed-off-by: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>