mmc: atmel-mci: adopt pinctrl support

Amend the atmel mci pin controller to optionally take a pin control
handle and set the state of the pins to:
- "default" on boot, resume and before performing an transfer.
- "sleep" on suspend().

This should make it possible to optimize energy usage for the pins
both for the suspend/resume cycle.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>