ARM: shmobile: Add r8a7791 legacy SDHI clocks

Add legacy r8a7791 SDHI clocks. This to allow the SDHI devices
to be used by legacy Koelsch board support.

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