clang-tidy: Fix override errors

The following errors were reported during the clang-tidy enablement
build due to overridden functions not being marked with the override
keyword. The proposed fix is to add the override keyword where it
was missing.

'''
1m../tools/i2c/i2c.hpp:176:10:
  error: 'open' overrides a member function but is not marked 'override' [-Werror
1m../tools/i2c/i2c.hpp:179:10:
  error: 'isOpen' overrides a member function but is not marked 'override' [-Werror
1m../tools/i2c/i2c.hpp:185:10:
   error: 'close' overrides a member function but is not marked 'override' [-Werror
'''

Tested: Verified Build and unit testing.

Change-Id: Iad01481761c6a4339e051c183c3dd238baf19d70
Signed-off-by: Jayanth Othayoth <ojayanth@gmail.com>
diff --git a/pmbus.hpp b/pmbus.hpp
index c798f51..6b5ccc4 100644
--- a/pmbus.hpp
+++ b/pmbus.hpp
@@ -320,7 +320,7 @@
      * @return vector<uint8_t> - The data read from the file.
      */
     std::vector<uint8_t> readBinary(const std::string& name, Type type,
-                                    size_t length);
+                                    size_t length) override;
 
     /**
      * Writes an integer value to the file, therefore doing