build: replace non open source path with QCPATH

QCPATH is an env variable defined and needs to be used
instead of non open source path.

Change-Id: I8b2a8d6caf50268bf12d80a7459aec312f95dbb5
diff --git a/BoardConfig.mk b/BoardConfig.mk
index 67eb091..134137e 100644
--- a/BoardConfig.mk
+++ b/BoardConfig.mk
@@ -10,7 +10,7 @@
 BOARD_USES_GENERIC_AUDIO := true
 USE_CAMERA_STUB := true
 
--include vendor/qcom/proprietary/common/msm8226/BoardConfigVendor.mk
+-include $(QCPATH)/common/msm8226/BoardConfigVendor.mk
 
 #TODO: For bring-up only; disable QC display path
 TARGET_BYPASS_QCUI := true