gpiolib: Add support for removing registered consumer lookup table

In case we unload and load a driver module again that is registering a
lookup table, without this it will result in multiple entries. Provide
an option to remove the lookup table on driver unload

Cc: Samuel Ortiz <sameo@linux.intel.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Alexandre Courbot <gnurou@gmail.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Reviewed-by: NAlexandre Courbot <acourbot@nvidia.com>
Reviewed-by: NLinus Walleij <linus.walleij@linaro.org>
Tested-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NShobhit Kumar <shobhit.kumar@intel.com>
Acked-by: NLee Jones <lee.jones@linaro.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpio/gpiolib.c

@@ -1672,6 +1672,19 @@ void gpiod_add_lookup_table(struct gpiod_lookup_table *table)
 	mutex_unlock(&gpio_lookup_lock);
 }
 
+/**
+ * gpiod_remove_lookup_table() - unregister GPIO device consumers
+ * @table: table of consumers to unregister
+ */
+void gpiod_remove_lookup_table(struct gpiod_lookup_table *table)
+{
+	mutex_lock(&gpio_lookup_lock);
+
+	list_del(&table->list);
+
+	mutex_unlock(&gpio_lookup_lock);
+}
+
 static struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
 				      unsigned int idx,
 				      enum gpio_lookup_flags *flags)

include/linux/gpio/machine.h

@@ -57,5 +57,6 @@ struct gpiod_lookup_table {
 }
 
 void gpiod_add_lookup_table(struct gpiod_lookup_table *table);
+void gpiod_remove_lookup_table(struct gpiod_lookup_table *table);
 
 #endif /* __LINUX_GPIO_MACHINE_H */