atmel-boards: add missing atmel_mci.h

commit 72fa467988 moved atmel_mci_init() into
include/atmel_mci.h. Some AT91 boards are also using this interface and need
to include atmel_mci.h now.

This patch fixes MAKEALL complaints like this:

---8<---
Configuring for ethernut5 - Board: ethernut5, Options: AT91SAM9XE
ethernut5.c: In function 'board_mmc_init':
ethernut5.c:235:2: warning: implicit declaration of function 'atmel_mci_init' [-Wimplicit-function-declaration]
--->8---

Signed-off-by: Andreas Bießmann <biessmann@corscience.de>
CC: Albert Aribaud <albert.u.boot@aribaud.net>
CC: Reinhard Meyer <u-boot@emk-elektronik.de>
CC: egnite GmbH <info@egnite.de>

board/egnite/ethernut5/ethernut5.c

@@ -77,6 +77,7 @@
 #include <spi.h>
 #include <dataflash.h>
 #include <mmc.h>
+#include <atmel_mci.h>
 
 #include <asm/arch/at91sam9260.h>
 #include <asm/arch/at91sam9260_matrix.h>

board/emk/top9000/top9000.c

@@ -29,6 +29,7 @@
 #include <net.h>
 #include <netdev.h>
 #include <mmc.h>
+#include <atmel_mci.h>
 #include <i2c.h>
 #include <spi.h>
 #include <asm/io.h>