hwmon: (pmbus/tps25990) Don't check for specific errors when parsing properties

hwmon: (pmbus/tps25990) Don't check for specific errors when parsing properties

Instead of checking for the specific error codes (that can be considered
a layering violation to some extent) check for the property existence first
and then either parse it, or apply a default value.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20260219141936.2259945-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>