mmc: renesas-sdhi: Wait after reconfiguring pins

The IP requires some time to recuperate after the IO pin
properties were changed. Add a delay to assure this.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>