hwmon: (pmbus/ibm-cffps) max_power_out swap changes

The bytes for max_power_out from the ibm-cffps devices differ in byte
order for some power supplies.

The Witherspoon power supply returns the bytes in MSB/LSB order.

The Rainier power supply returns the bytes in LSB/MSB order.

The Witherspoon power supply uses version cffps1. The Rainier power
supply should use version cffps2. If version is cffps1, swap the bytes
before output to max_power_out.

Tested:
    Witherspoon before: 3148. Witherspoon after: 3148.
    Rainier before: 53255. Rainier after: 2000.
Signed-off-by: Brandon Wyman <bjwyman@gmail.com>
Reviewed-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20210928205051.1222815-1-bjwyman@gmail.com
[groeck: Replaced yoda programming]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/pmbus/ibm-cffps.c

@@ -171,8 +171,14 @@ static ssize_t ibm_cffps_debugfs_read(struct file *file, char __user *buf,
 		cmd = CFFPS_SN_CMD;
 		break;
 	case CFFPS_DEBUGFS_MAX_POWER_OUT:
-		rc = i2c_smbus_read_word_swapped(psu->client,
-						 CFFPS_MAX_POWER_OUT_CMD);
+		if (psu->version == cffps1) {
+			rc = i2c_smbus_read_word_swapped(psu->client,
+					CFFPS_MAX_POWER_OUT_CMD);
+		} else {
+			rc = i2c_smbus_read_word_data(psu->client,
+					CFFPS_MAX_POWER_OUT_CMD);
+		}
+
 		if (rc < 0)
 			return rc;