device: Const-ify all device driver instance pointers

Now that device_api attribute is unmodified at runtime, as well as all
the other attributes, it is possible to switch all device driver
instance to be constant.

A coccinelle rule is used for this:

@r_const_dev_1
  disable optional_qualifier
@
@@
-struct device *
+const struct device *

@r_const_dev_2
 disable optional_qualifier
@
@@
-struct device * const
+const struct device *

Fixes #27399

Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>

include/fs/nvs.h

@@ -55,7 +55,7 @@ struct nvs_fs {
 	bool ready;		/* is the filesystem initialized ? */
 
 	struct k_mutex nvs_lock;
-	struct device *flash_device;
+	const struct device *flash_device;
 	const struct flash_parameters *flash_parameters;
 };