Revert "nvmem: core: remove nvmem_config wp_gpio"

This reverts commit 6d9fa3ff65 which is
commit 569653f022a29a1a44ea9de5308b657228303fa5 upstream.

It breaks the kernel abi and is not needed in Android systems at this
point in time.

If it's wanted, it can come back in an abi-safe way in the future.

Bug: 161946584
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I75ba9754039f961a77c1d04f22c9110287cd8efe

drivers/nvmem/core.c

@@ -768,7 +768,9 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
 
 	nvmem->id = rval;
 
-	if (!config->ignore_wp)
+	if (config->wp_gpio)
+		nvmem->wp_gpio = config->wp_gpio;
+	else if (!config->ignore_wp)
 		nvmem->wp_gpio = gpiod_get_optional(config->dev, "wp",
 						    GPIOD_OUT_HIGH);
 	if (IS_ERR(nvmem->wp_gpio)) {

include/linux/nvmem-provider.h

@@ -66,6 +66,7 @@ struct nvmem_keepout {
  * @word_size:	Minimum read/write access granularity.
  * @stride:	Minimum read/write access stride.
  * @priv:	User context passed to read/write callbacks.
+ * @wp-gpio:	Write protect pin
  * @ignore_wp:  Write Protect pin is managed by the provider.
  *
  * Note: A default "nvmem<id>" name will be assigned to the device if
@@ -80,6 +81,7 @@ struct nvmem_config {
 	const char		*name;
 	int			id;
 	struct module		*owner;
+	struct gpio_desc	*wp_gpio;
 	const struct nvmem_cell_info	*cells;
 	int			ncells;
 	const struct nvmem_keepout *keepout;