clang updates

The openbmc CI was recently updated to clang-12 which requires some
formatting updates to the code:
https://github.com/openbmc/openbmc-build-scripts/commit/4569bf49daaebff06be0482426908bb5497fad08

Make those updates and refresh the clang-format file with the one from
docs:
https://github.com/openbmc/docs/blob/master/style/cpp/.clang-format

Change-Id: Ieb3626526373a053ec84431e7560003f229f338d
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/file_descriptor.hpp b/file_descriptor.hpp
index 7929aa6..4b98aea 100644
--- a/file_descriptor.hpp
+++ b/file_descriptor.hpp
@@ -29,8 +29,7 @@
      * @param[in] fd - File descriptor
      */
     FileDescriptor(int fd) : fd(fd)
-    {
-    }
+    {}
 
     /**
      * Move constructor.