mmc: atmel-mci: Switch to using managed resource in probe

This change uses managed resource APIs to allocate resources such as,
clk, gpio, io in order to simplify the driver unload or failure cases.
Hence does away with release statements of the same resources in error
labels and remove function.

Signed-off-by: Pramod Gurav <pramod.gurav@smartplayin.com>
Acked-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>