linux-user: Clean up target_cpu.h header guards

These headers all use TARGET_CPU_H as header guard symbol.  Reuse of
the same guard symbol in multiple headers is okay as long as they
cannot be included together.

Since we can avoid guard symbol reuse easily, do so: use guard symbol
$target_TARGET_CPU_H for linux-user/$target/target_cpu.h.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>

linux-user/mips/target_cpu.h

@@ -16,8 +16,8 @@
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  */
-#ifndef TARGET_CPU_H
-#define TARGET_CPU_H
+#ifndef MIPS_TARGET_CPU_H
+#define MIPS_TARGET_CPU_H
 
 static inline void cpu_clone_regs(CPUMIPSState *env, target_ulong newsp)
 {