hwmon: (pmbus/mp2975) Add missed POUT attribute for page 1 mp2975 controller

Add missed attribute for reading POUT from page 1.
It is supported by device, but has been missed in initial commit.

Fixes: 2c6fcbb2 ("hwmon: (pmbus) Add support for MPS Multi-phase mp2975 controller")
Signed-off-by: NVadim Pasternak <vadimp@nvidia.com>
Link: https://lore.kernel.org/r/20210927070740.2149290-1-vadimp@nvidia.comSigned-off-by: NGuenter Roeck <linux@roeck-us.net>

drivers/hwmon/pmbus/mp2975.c

@@ -54,7 +54,7 @@
 
 #define MP2975_RAIL2_FUNC	(PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT | \
 				 PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT | \
-				 PMBUS_PHASE_VIRTUAL)
+				 PMBUS_HAVE_POUT | PMBUS_PHASE_VIRTUAL)
 
 struct mp2975_data {
 	struct pmbus_driver_info info;