drm/amdgpu: add determine passthrough under arm64

add determine for passthrough mode under arm64 by reading
CurrentEL register

v2: squash in warning fix (Alex)
Signed-off-by: Victor Zhao <Victor.Zhao@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_virt.h

@@ -294,8 +294,10 @@ struct amdgpu_video_codec_info;
 
 static inline bool is_virtual_machine(void)
 {
-#ifdef CONFIG_X86
+#if defined(CONFIG_X86)
 	return boot_cpu_has(X86_FEATURE_HYPERVISOR);
+#elif defined(CONFIG_ARM64)
+	return !is_kernel_in_hyp_mode();
 #else
 	return false;
 #endif