ARM: at91/dt: sama5d4ek: mci0 uses slot 0

Mci0 uses slot 0 not 1.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Fixes: 7a475267 ("ARM: at91: dt: add device tree file for SAMA5D4ek board")
Cc: stable@vger.kernel.org
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>