arm: am335x-pdu001: Move from embedded to separate DTB

There is no need for an embedded device tree for this board so let the
build process generate a separate u-boot.dtb file instead.

Signed-off-by: Felix Brack <fb@ltec.ch>
diff --git a/arch/arm/mach-omap2/am33xx/Kconfig b/arch/arm/mach-omap2/am33xx/Kconfig
index 3529607..57284c4 100644
--- a/arch/arm/mach-omap2/am33xx/Kconfig
+++ b/arch/arm/mach-omap2/am33xx/Kconfig
@@ -206,6 +206,7 @@
 	bool "Support PDU001"
 	select DM
 	select DM_SERIAL
+	imply SPL_SEPARATE_BSS
 	imply CMD_DM
 	help
 	  Support for PDU001 platform developed by EETS GmbH.