clk: sunxi: sun9i-mmc: Implement reset callback for reset controls

clk: sunxi: sun9i-mmc: Implement reset callback for reset controls

commit 61d2f2a05765a5f57149efbd93e3e81a83cbc2c1 upstream.

Our MMC host driver now issues a reset, instead of just deasserting
the reset control, since commit c34eda69ad4c ("mmc: sunxi: Reset the
device at probe time"). The sun9i-mmc clock driver does not support
this, and will fail, which results in MMC not probing.

This patch implements the reset callback by asserting the reset control,
then deasserting it after a small delay.

Fixes: 7a6fca879f59 ("clk: sunxi: Add driver for A80 MMC config clocks/resets")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
Link: lkml.kernel.org/r/20171218035751.20661-1-wens@csie.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>