hwmon: (ina3221) Add averaging mode support

The CONFIG register has a 3-bit averaging mode field for users
to setup the number of samples that are collected and averaged
together. This is very useful to filter noise from sensor data.

This patch adds a 'samples' sysfs node using hwmon_chip_samples
of hwmon core, and updates wait time calculation by taking this
samples value into account.

Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
diff --git a/Documentation/hwmon/ina3221 b/Documentation/hwmon/ina3221
index 4b82cbf..ed3f227 100644
--- a/Documentation/hwmon/ina3221
+++ b/Documentation/hwmon/ina3221
@@ -35,3 +35,6 @@
                           average is above this value.
 curr[123]_max_alarm     Warning alert current limit exceeded
 in[456]_input           Shunt voltage(uV) for channels 1, 2, and 3 respectively
+samples                 Number of samples using in the averaging mode.
+                          Supports the list of number of samples:
+                          1, 4, 16, 64, 128, 256, 512, 1024