ARM: shmobile: Use r8a7791_add_standard_devices() on Koelsch

Use r8a7791_add_standard_devices() on Koelsch to let
the C version of the board code add on-chip devices.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>