sh: Rename sci_ick and sci_fck clock to fck

The SCI driver requires a functional clock named "fck" and falls back to
"sci_ick" or "sci_fck" when the "fck" clock doesn't exist. To allow
removal of the fallback code rename the sci_ick and sci_fck clocks to
fck for all SH platforms.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>