target/mips: Constify all Property

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

target/mips/cpu.c

@@ -539,7 +539,7 @@ static const struct SysemuCPUOps mips_sysemu_ops = {
 };
 #endif
 
-static Property mips_cpu_properties[] = {
+static const Property mips_cpu_properties[] = {
     DEFINE_PROP_BOOL("big-endian", MIPSCPU, is_big_endian, TARGET_BIG_ENDIAN),
     DEFINE_PROP_END_OF_LIST(),
 };