ARM: atmel: sama5d4: build related file when enable SPL

Signed-off-by: Bo Shen <voice.shen@atmel.com>
diff --git a/arch/arm/cpu/at91-common/Makefile b/arch/arm/cpu/at91-common/Makefile
index 89e1577..03614d4 100644
--- a/arch/arm/cpu/at91-common/Makefile
+++ b/arch/arm/cpu/at91-common/Makefile
@@ -13,5 +13,6 @@
 obj-$(CONFIG_AT91SAM9G20) += sdram.o spl_at91.o
 obj-$(CONFIG_AT91SAM9M10G45) += mpddrc.o spl_at91.o
 obj-$(CONFIG_SAMA5D3) += mpddrc.o spl_atmel.o
+obj-$(CONFIG_SAMA5D4) += mpddrc.o spl_atmel.o
 obj-y += spl.o
 endif