mci: sdhci: implement sdhci_reset() ...

SDHCI reset is common between many SDHCI variants. Add a library
function, so it can be reused.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

mci: imx-esdhc-pbl: Use sdhci_transfer_data() ...

Drop some extra code by converting esdhc_do_data() to use
sdhci_transfer_data().

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

mci: Add sdhci helper ...

We have several SDHCI compatible drivers in the tree. This starts
with a set of generic helper functions for these drivers to share
some common functionality.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>