coresight: etm4x: Fix mis-usage of nr_resource in sysfs interface

The member @nr_resource represents how many resource selector pairs,
and the pair 0 is always implemented and reserved.
So let's multiply by 2 when resetting the selector configuration.
And also update the validation of the input @idx.

Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Shaokun Zhang <zhangshaokun@hisilicon.com>
Signed-off-by: Jonathan Zhou <jonathan.zhouwen@huawei.com>
[Fixed typographical error in changelog, added stable]
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200916191737.4001561-16-mathieu.poirier@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/coresight/coresight-etm4x-sysfs.c

@@ -236,7 +236,7 @@ static ssize_t reset_store(struct device *dev,
 	}
 
 	config->res_idx = 0x0;
-	for (i = 0; i < drvdata->nr_resource; i++)
+	for (i = 2; i < 2 * drvdata->nr_resource; i++)
 		config->res_ctrl[i] = 0x0;
 
 	config->ss_idx = 0x0;
@@ -1663,8 +1663,11 @@ static ssize_t res_idx_store(struct device *dev,
 
 	if (kstrtoul(buf, 16, &val))
 		return -EINVAL;
-	/* Resource selector pair 0 is always implemented and reserved */
-	if ((val == 0) || (val >= drvdata->nr_resource))
+	/*
+	 * Resource selector pair 0 is always implemented and reserved,
+	 * namely an idx with 0 and 1 is illegal.
+	 */
+	if ((val < 2) || (val >= 2 * drvdata->nr_resource))
 		return -EINVAL;
 
 	/*