mmc: sh_mmcif: remove unneeded clock connection ID

MMCIF only uses one clock, all ARM and SuperH platforms register MMCIF
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>