nios2: Move individual board linker scripts to common script in cpu tree.

Signed-off-by: Scott McNutt <smcnutt@psyent.com>
diff --git a/arch/nios2/config.mk b/arch/nios2/config.mk
index be40639..f455982 100644
--- a/arch/nios2/config.mk
+++ b/arch/nios2/config.mk
@@ -28,3 +28,5 @@
 
 PLATFORM_CPPFLAGS += -DCONFIG_NIOS2 -D__NIOS2__
 PLATFORM_CPPFLAGS += -ffixed-r15 -G0
+
+LDSCRIPT := $(SRCTREE)/$(CPUDIR)/u-boot.lds