arm: atmel: sama5d3: add spi spl boot support

Add SPI SPL boot support for sama5d3xek board.

Signed-off-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>
diff --git a/board/atmel/sama5d3xek/sama5d3xek.c b/board/atmel/sama5d3xek/sama5d3xek.c
index eff94a4..8a214de 100644
--- a/board/atmel/sama5d3xek/sama5d3xek.c
+++ b/board/atmel/sama5d3xek/sama5d3xek.c
@@ -307,6 +307,8 @@
 {
 #ifdef CONFIG_SYS_USE_MMC
 	sama5d3xek_mci_hw_init();
+#elif CONFIG_SYS_USE_SERIALFLASH
+	at91_spi0_hw_init(1 << 0);
 #endif
 }