powerpc/85xx: Remove config.mk for nand linker script

Move the include of mpc85xx/u-boot-nand.lds to utilize
CONFIG_SYS_LDSCRIPT rather than having an explicit config.mk

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/include/configs/MPC8572DS.h b/include/configs/MPC8572DS.h
index bf2fdd6..4224229 100644
--- a/include/configs/MPC8572DS.h
+++ b/include/configs/MPC8572DS.h
@@ -40,6 +40,7 @@
 #define CONFIG_SYS_TEXT_BASE_SPL 0xfff00000
 #define CONFIG_SYS_MONITOR_BASE	CONFIG_SYS_TEXT_BASE_SPL /* start of monitor */
 #else
+#define CONFIG_SYS_LDSCRIPT $(TOPDIR)/$(CPUDIR)/u-boot-nand.lds
 #define CONFIG_SYS_TEXT_BASE	0xf8f82000
 #endif /* CONFIG_NAND_SPL */
 #endif