pinctrl: generic: update references to Documentation/pinctrl.txt

Update deprecated references to Documentation/pinctrl.txt since it has been
moved to Documentation/driver-api/pinctl.rst.

Signed-off-by: Ludovic Desroches <ludovic.desroches@o2linux.fr>
Fixes: 5a9b73832e9e ("pinctrl.txt: move it to the driver-api book")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/include/linux/device.h b/include/linux/device.h
index 723cd54..beabdbc 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -843,7 +843,7 @@
  * 		hibernation, system resume and during runtime PM transitions
  * 		along with subsystem-level and driver-level callbacks.
  * @pins:	For device pin management.
- *		See Documentation/pinctrl.txt for details.
+ *		See Documentation/driver-api/pinctl.rst for details.
  * @msi_list:	Hosts MSI descriptors
  * @msi_domain: The generic MSI domain this device is using.
  * @numa_node:	NUMA node this device is close to.