hikey: add mtools installation to README

Change-Id: I8a1f561ff27193aee673ed166076e13ca5637cc4
Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>
diff --git a/README b/README
index 8aabe49..9425f02 100644
--- a/README
+++ b/README
@@ -9,6 +9,9 @@
 $ tar xzf linaro-hikey-20160226-67c37b1a.tgz
 $ ./extract-linaro-hikey.sh
 
+Install mcopy utility:
+$ apt-get install mtools
+
 Build:
 $ . ./build/envsetup.sh
 $ lunch hikey-userdebug