nvmem: core: make nvmem_layout_bus_type const

Since commit d492cc25 ("driver core: device.h: make struct bus_type
a const *"), the driver core can properly handle constant struct
bus_type, move the nvmem_layout_bus_type variable to be a constant
structure as well, placing it into read-only memory which can not be
modified at runtime.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: "Ricardo B. Marliere" <ricardo@marliere.net>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20240224114516.86365-11-srinivas.kandagatla@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/layouts.c

@@ -45,7 +45,7 @@ static void nvmem_layout_bus_remove(struct device *dev)
 	return drv->remove(layout);
 }
 
-static struct bus_type nvmem_layout_bus_type = {
+static const struct bus_type nvmem_layout_bus_type = {
 	.name		= "nvmem-layout",
 	.match		= nvmem_layout_bus_match,
 	.probe		= nvmem_layout_bus_probe,