platform/x86: intel-uncore-freq: Conditionally create attribute for read frequency

When the current uncore frequency can't be read, don't create attribute
"current_freq_khz" as any read will fail later. Some user space
applications like turbostat fail to continue with the failure. So, check
error during attribute creation.

Fixes: 414eef27283a ("platform/x86/intel/uncore-freq: Display uncore current frequency")
Signed-off-by: Srinivas Pandruvada <[e-mail]>
Reviewed-by: Ilpo Järvinen <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Hans de Goede <[e-mail]>
Signed-off-by: Hans de Goede <[e-mail]>

drivers/platform/x86/intel/uncore-frequency/uncore-frequency-common.c

···
 
 static int create_attr_group(struct uncore_data *data, char *name)
 {
-	int ret, index = 0;
+	int ret, freq, index = 0;
 
 	init_attribute_rw(max_freq_khz);
 	init_attribute_rw(min_freq_khz);
···
 	data->uncore_attrs[index++] = &data->min_freq_khz_dev_attr.attr;
 	data->uncore_attrs[index++] = &data->initial_min_freq_khz_dev_attr.attr;
 	data->uncore_attrs[index++] = &data->initial_max_freq_khz_dev_attr.attr;
-	data->uncore_attrs[index++] = &data->current_freq_khz_dev_attr.attr;
+
+	ret = uncore_read_freq(data, &freq);
+	if (!ret)
+		data->uncore_attrs[index++] = &data->current_freq_khz_dev_attr.attr;
+
 	data->uncore_attrs[index] = NULL;
 
 	data->uncore_attr_group.name = name;