ARM: shmobile: Koelsch support

Koelsch base board support making use of 2 GiB of memory,
the r8a7791 SoC with the SCIF0 serial port and CA15 with
CMT timer.

Signed-off-by: Hisashi Nakamura <hisashi.nakamura.ak@renesas.com>
Signed-off-by: Ryo Kataoka <ryo.kataoka.wt@renesas.com>
[damm@opensource.se: Forward ported to upstream, dropped not-yet-ready SMP/PFC]
Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>