mmc: tmio: remove SCLKEN bit setting from tmio_mmc_set_clock()

TMIO clock is set via tmio_mmc_set_clock() -> tmio_mmc_clk_start(),
and SCLKEN bit will be set on tmio_mmc_clk_start().
It is not needed on tmio_mmc_set_clock() function.
The required clock setting will not be able to set
in some clocks without this patch.

Tested-by: Nguyen Xuan Nui <nx-nui@jinso.co.jp>
Tested-by: Hiep Cao Minh <cm-hiep@jinso.co.jp>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>