target/arm: Rebuild hflags at EL changes

Begin setting, but not relying upon, env->hflags.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20191023150057.25731-17-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

linux-user/syscall.c

@@ -9984,6 +9984,7 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
                     aarch64_sve_narrow_vq(env, vq);
                 }
                 env->vfp.zcr_el[1] = vq - 1;
+                arm_rebuild_hflags(env);
                 ret = vq * 16;
             }
             return ret;