sh: sh7722: fix Oops: remove empty clock entries

Unused indices produce empty entries in the clock array, which then lead to
Oopses at boot-time.

Reported-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>