ASoC: rcar: remove unnecessary mach/clock.h

${LINUX}/sound/soc/sh driver can be compiled from
SuperH and ARM.
but, ${LINUX}/sound/soc/sh/rcar driver included
SH-ARM specific header.
This patch removes it

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@linaro.org>