[D1s]Add mksdcard.sh

bsp/allwinner/d1s/mksdcard.sh

@@ -0,0 +1,7 @@
+if [ ! -f "sdroot.bin" ]; then
+dd if=/dev/zero of=sdroot.bin bs=1M count=4
+fi
+
+mkfs.fat sdroot.bin
+mcopy -i sdroot.bin root/bin/* ::
+