base: Fix include order in the inifile unit test.

base: Fix include order in the inifile unit test.

Even though gtest.h is a C++ header, it looks like a C header which
makes the style check hook upset. Lets move it up so the hook doesn't
complain when the file is changed.

Change-Id: Ibcc2d0b7bf3b254c70e55b30379ebd4b70933c26
Reviewed-on: https://gem5-review.googlesource.com/c/14675
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>