janitor: add guards to headers

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/tcg/mips/tcg-target.h b/tcg/mips/tcg-target.h
index 65b5c59..78af664 100644
--- a/tcg/mips/tcg-target.h
+++ b/tcg/mips/tcg-target.h
@@ -23,6 +23,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
+#ifndef TCG_TARGET_MIPS 
 #define TCG_TARGET_MIPS 1
 
 #ifdef __MIPSEB__
@@ -127,3 +128,5 @@
 {
     cacheflush ((void *)start, stop-start, ICACHE);
 }
+
+#endif