configure.sh: update custom board config build

If Make.defs not found under boardconfig dir, then try
scripts/Make.defs.

Signed-off-by: liuhaitao <liuhaitao@xiaomi.com>

tools/configure.sh

@@ -164,11 +164,15 @@ if [ ! -r ${src_makedefs} ]; then
 
   if [ ! -r ${src_makedefs} ]; then
     src_makedefs=${TOPDIR}/${boardconfig}/Make.defs
+    if [ ! -r ${src_makedefs} ]; then
+      src_makedefs=${TOPDIR}/${boardconfig}/../../scripts/Make.defs
+
       if [ ! -r ${src_makedefs} ]; then
         echo "File Make.defs could not be found"
         exit 4
       fi
     fi
+  fi
 fi
 
 src_config=${configpath}/defconfig