Added data submodule

Change-Id: Ib9554b4005190e06761af217befe824b9baaaf88
Signed-off-by: Gian Marco Iodice <gianmarco.iodice@arm.com>
diff --git a/.gitmodules b/.gitmodules
index e69de29..011141e 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -0,0 +1,4 @@
+[submodule "data"]
+    path = data
+    url = https://git.research.arm.com/ComputeLibrary/data.git
+    branch = master