hwmon: (ltc2992) Set `can_sleep` flag for GPIO chip

The ltc2992 drivers uses a mutex and I2C bus access in its GPIO chip `set`
and `get` implementation. This means these functions can sleep and the GPIO
chip should set the `can_sleep` property to true.

This will ensure that a warning is printed when trying to set or get the
GPIO value from a context that potentially can't sleep.

Fixes: 9ca26df1 ("hwmon: (ltc2992) Add support for GPIOs.")
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Link: https://lore.kernel.org/r/20230314093146.2443845-2-lars@metafoo.deSigned-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/ltc2992.c

@@ -323,6 +323,7 @@ static int ltc2992_config_gpio(struct ltc2992_state *st)
 	st->gc.label = name;
 	st->gc.parent = &st->client->dev;
 	st->gc.owner = THIS_MODULE;
+	st->gc.can_sleep = true;
 	st->gc.base = -1;
 	st->gc.names = st->gpio_names;
 	st->gc.ngpio = ARRAY_SIZE(st->gpio_names);