vexpress: Set toolchain in Boardconfig.mk

We need not export the TARGET_TOOLS_PREFIX before building.
The patch is dependent on http://review.android.git.linaro.org/#/c/4430/

Change-Id: I09e2c9ead4811be0a1b1d6d4a958e03443700429
Signed-off-by: Vishal Bhoj <vishal.bhoj@linaro.org>
diff --git a/BoardConfig.mk b/BoardConfig.mk
index ae9f8dd..af40ee1 100644
--- a/BoardConfig.mk
+++ b/BoardConfig.mk
@@ -83,6 +83,7 @@
 #
 # MP
 #
+include $(TOPDIR)device/linaro/common/linaro_configs.mk
 KERNEL_CONFIG ?= linaro/configs/linaro-base.conf \
                  linaro/configs/android.conf \
                  linaro/configs/big-LITTLE-MP.conf \