arm: atmel: sama5d3: spl boot from fat fs SD card

Enable Atmel sama5d3xek boart spl boot support, which can load u-boot
from SD card with FAT file system.

Signed-off-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>
diff --git a/arch/arm/cpu/at91-common/Makefile b/arch/arm/cpu/at91-common/Makefile
index 671a05e..d97053f 100644
--- a/arch/arm/cpu/at91-common/Makefile
+++ b/arch/arm/cpu/at91-common/Makefile
@@ -8,4 +8,4 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-obj-$(CONFIG_SPL_BUILD) += mpddrc.o
+obj-$(CONFIG_SPL_BUILD) += mpddrc.o spl.o