clang-tidy: Enable modernize-use-override check

This check adds override (introduced in C++11) to overridden
virtual functions and removes virtual from those functions as it
is not required.

Change-Id: I156fc5796ed1cf451491e446c211172f62316ecc
Signed-off-by: Pavithra Barithaya <pavithrabarithaya07@gmail.com>
diff --git a/.clang-tidy b/.clang-tidy
index b816a4e..c382910 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -221,6 +221,7 @@
 modernize-use-equals-default,
 modernize-use-equals-delete,
 modernize-use-noexcept,
+modernize-use-override,
 modernize-use-transparent-functors,
 modernize-use-uncaught-exceptions,
 modernize-use-using'