target-arm: Add feature unset function

Add an unset_feature() function to compliment the set_feature() function.  This
will be used to disable functions after they have been enabled during
initialization.
Signed-off-by: NGreg Bellows <greg.bellows@linaro.org>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Message-id: 1418684992-8996-9-git-send-email-greg.bellows@linaro.org
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

target-arm/cpu.c

@@ -327,6 +327,11 @@ static inline void set_feature(CPUARMState *env, int feature)
     env->features |= 1ULL << feature;
 }
 
+static inline void unset_feature(CPUARMState *env, int feature)
+{
+    env->features &= ~(1ULL << feature);
+}
+
 static void arm_cpu_initfn(Object *obj)
 {
     CPUState *cs = CPU(obj);