at91: port legacy at91_mci driver

Signed-off-by: Patrice Vilchez <patrice.vilchez@atmel.com>
at91sam9rlek: enable at91_mci legacy driver

Signed-off-by: Patrice Vilchez <patrice.vilchez@atmel.com>
at91: sam9rl: update defconfig file

Signed-off-by: Patrice Vilchez <patrice.vilchez@atmel.com>