mmc: sh_mobile_sdhi: remove unneeded clock connection ID

SDHI only uses one clock, all ARM and SuperH platform register SDHI clock
lookup entries with no connection ID, hence it can be dropped in the
driver too.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Chris Ball <cjb@laptop.org>