fdt: Swap the signature for board_fdt_blob_setup()

This returns a devicetree and updates a parameter with an error code.
Swap it, since this fits better with the way U-Boot normally works. It
also (more easily) allows leaving the existing pointer unchanged.

No yaks were harmed in this change, but there is a very small code-size
reduction.

For sifive, the OF_BOARD option must be set for the function to be
called, so there is no point in checking it again. Also OF_SEPARATE is
defined always.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Matthias Brugger <mbrugger@suse.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
[trini: Update total_compute]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/board/andestech/ae350/ae350.c b/board/andestech/ae350/ae350.c
index 5ae5bae..1d9d4a9 100644
--- a/board/andestech/ae350/ae350.c
+++ b/board/andestech/ae350/ae350.c
@@ -79,21 +79,24 @@
 }
 
 #define ANDES_HW_DTB_ADDRESS	0xF2000000
-void *board_fdt_blob_setup(int *err)
+int board_fdt_blob_setup(void **fdtp)
 {
-	*err = 0;
-
 	if (IS_ENABLED(CONFIG_OF_SEPARATE) || IS_ENABLED(CONFIG_OF_BOARD)) {
-		if (fdt_magic((uintptr_t)gd->arch.firmware_fdt_addr) == FDT_MAGIC)
-			return (void *)(ulong)gd->arch.firmware_fdt_addr;
+		if (fdt_magic((uintptr_t)gd->arch.firmware_fdt_addr) ==
+			FDT_MAGIC) {
+			*fdtp = (void *)(ulong)gd->arch.firmware_fdt_addr;
+
+			return 0;
+		}
 	}
 
-	if (fdt_magic(CONFIG_SYS_FDT_BASE) == FDT_MAGIC)
-		return (void *)CONFIG_SYS_FDT_BASE;
-	return (void *)ANDES_HW_DTB_ADDRESS;
+	if (fdt_magic(CONFIG_SYS_FDT_BASE) == FDT_MAGIC) {
+		*fdtp = (void *)CONFIG_SYS_FDT_BASE;
+
+		return 0;
+	}
 
-	*err = -EINVAL;
-	return NULL;
+	return -EINVAL;
 }
 
 #ifdef CONFIG_SPL_BOARD_INIT