ARM: at91: sama5d3xek: use a $dtb_name to load dtb

Since sama5d3xek boards has different type of dtb blobs, so we need to detect
the cpu type in runtime.

So we add a new variable $dtb_name. if $dtb_name is not defined, we just use
	at91-${board_name}.dtb

as the $dtb_name. Otherwise, we will just load the dtb with
	$dtb_name.

For sama5d3xek, we will detect cpu type and make up $dtb_name in
runtime.

Signed-off-by: Josh Wu <josh.wu@atmel.com>
diff --git a/board/atmel/sama5d3xek/sama5d3xek.c b/board/atmel/sama5d3xek/sama5d3xek.c
index 2bd436a..7c95f33 100644
--- a/board/atmel/sama5d3xek/sama5d3xek.c
+++ b/board/atmel/sama5d3xek/sama5d3xek.c
@@ -15,6 +15,7 @@
 #include <asm/arch/gpio.h>
 #include <asm/arch/clk.h>
 #include <lcd.h>
+#include <linux/ctype.h>
 #include <atmel_hlcdc.h>
 #include <atmel_mci.h>
 #include <phy.h>
@@ -369,6 +370,25 @@
 }
 #endif /* CONFIG_ATMEL_SPI */
 
+#ifdef CONFIG_BOARD_LATE_INIT
+int board_late_init(void)
+{
+#ifdef CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
+	const int MAX_STR_LEN = 32;
+	char name[MAX_STR_LEN], *p;
+	int i;
+
+	strncpy(name, get_cpu_name(), MAX_STR_LEN);
+	for (i = 0, p = name; (*p) && (i < MAX_STR_LEN); p++, i++)
+		*p = tolower(*p);
+
+	strcat(name, "ek.dtb");
+	setenv("dtb_name", name);
+#endif
+	return 0;
+}
+#endif
+
 /* SPL */
 #ifdef CONFIG_SPL_BUILD
 void spl_board_init(void)