Introduce clang-format

An automated and opinionated style for code. We can decide to change the
style and have the source updated by the clang-format tool by running:

    make format

I've based the style on the Google style with exceptions to better
match
the current source style.

Change-Id: I43f85c7d4ce02ca999805558b25fcab2e43859c6
diff --git a/inc/vm.h b/inc/vm.h
index 88ae8ac..eb6a386 100644
--- a/inc/vm.h
+++ b/inc/vm.h
@@ -13,4 +13,4 @@
 void vm_start_vcpu(struct vm *vm, size_t index, size_t entry, size_t arg,
 		   bool is_primary);
 
-#endif  /* _VM_H */
+#endif /* _VM_H */