gpio: shared: fix NULL-pointer dereference in teardown path

We need to actually store the address of the GPIO lookup table in the
reference struct before we try to free it or - worse - dereference its
members.

Fixes: a060b8c ("gpiolib: implement low-level, shared GPIO support")
Link: https://lore.kernel.org/r/20251206-gpio-shared-teardown-fixes-v1-1-35ac458cfce1@oss.qualcomm.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>

Author: Bartosz Golaszewski

drivers/gpio/gpiolib-shared.c

@@ -399,7 +399,8 @@ int gpio_shared_add_proxy_lookup(struct device *consumer, unsigned long lflags)
 			lookup->table[0] = GPIO_LOOKUP(no_free_ptr(key), 0,
 						       ref->con_id, lflags);
 
-			gpiod_add_lookup_table(no_free_ptr(lookup));
+			ref->lookup = no_free_ptr(lookup);
+			gpiod_add_lookup_table(ref->lookup);
 
 			return 0;
 		}