hwmon: (pmbus/adm1266) register the gpio_chip after pmbus_do_probe()

hwmon: (pmbus/adm1266) register the gpio_chip after pmbus_do_probe()

adm1266_probe() calls adm1266_config_gpio() -- which goes on to
devm_gpiochip_add_data() and exposes the gpio_chip callbacks to
gpiolib -- before pmbus_do_probe() has initialised the per-client
PMBus state (notably the pmbus_lock mutex the core hands out via
pmbus_get_data()).

That ordering is already a latent hazard: any GPIO access that lands
between adm1266_config_gpio() and the end of pmbus_do_probe() (for
example a sysfs read from a user space agent that opens the gpiochip
the instant gpiolib advertises it) races pmbus_do_probe()'s own
device accesses with no serialisation.

Move adm1266_config_gpio() down past pmbus_do_probe() so the chip
isn't reachable from userspace until the PMBus state it depends on
is fully initialised.

Fixes: d98dfad35c38 ("hwmon: (pmbus/adm1266) Add support for GPIOs")
Cc: stable@vger.kernel.org
Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20260518-adm1266-gpio-fixes-v3-4-e425e4f88139@nexthop.ai
Signed-off-by: Guenter Roeck <linux@roeck-us.net>