Blackfin: fix out-of-tree building with ldscripts

Many of the Blackfin board linker scripts are preprocessed, so make sure we
output the linker script into the build tree rather than the source tree.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/board/bf533-stamp/config.mk b/board/bf533-stamp/config.mk
index 9847924..c8b9fb8 100644
--- a/board/bf533-stamp/config.mk
+++ b/board/bf533-stamp/config.mk
@@ -26,6 +26,8 @@
 # This is not actually used for Blackfin boards so do not change it
 #TEXT_BASE = do-not-use-me
 
+LDSCRIPT = $(obj)board/$(BOARDDIR)/u-boot.lds
+
 # Set some default LDR flags based on boot mode.
 LDR_FLAGS-BFIN_BOOT_PARA := --bits 16 --dma 8
 LDR_FLAGS += $(LDR_FLAGS-$(CONFIG_BFIN_BOOT_MODE))