mmc: sh_mmcif: Use "kHz" for kilohertz

"K" stands for "kelvin".

While at it, make the spacing before units consistent.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20200618080321.16678-1-geert+renesas@glider.be


Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>