Add clang format for C and C++

The libpldm is written in C and can be shared with projects other than
OpenBMC. The code written in C follows the Linux kernel coding guidelines.
The libpldmresponder and the application code follows the modern C++ and the
clang format follows the OpenBMC coding guidelines.

clang-format for each input file will try to find the .clang-format file
located in the closest parent directory of the input file. Since the C code is
in libpldm directory it has a specific .clang-format.

Change-Id: I9346d454cb20009c6daf526d4ceb722d7400a8d1
Signed-off-by: Tom Joseph <tomjoseph@in.ibm.com>