docs: driver-model: move it to the driver-api book

The audience for the Kernel driver-model is clearly Kernel hackers.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com> # ice driver changes
diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 7139032..506a017 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -5,7 +5,7 @@
  * Copyright (c) 2002-3 Patrick Mochel
  * Copyright (c) 2002-3 Open Source Development Labs
  *
- * Please see Documentation/driver-model/platform.rst for more
+ * Please see Documentation/driver-api/driver-model/platform.rst for more
  * information.
  */