nvmem: release the write-protect pin

Put the write-protect GPIO descriptor in nvmem_release() so that it can
be automatically released when the associated device's reference count
drops to 0.

Fixes: 2a127da4 ("nvmem: add support for the write-protect pin")
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Khouloud Touil <ktouil@baylibre.com>
Cc: stable <stable@vger.kernel.org>
[Bartosz: tweak the commit message]
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20200310132257.23358-8-srinivas.kandagatla@linaro.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>