nvmem: core: Set the provider read-only when no write callback is given

If no write callback is given the device should be marked as read-only.
While at it also move from a bit or to a logical or as that is a logical
expression.

Signed-off-by: Alban Bedel <albeu@free.fr>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/core.c

@@ -646,8 +646,8 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
 			     config->name ? config->id : nvmem->id);
 	}
 
-	nvmem->read_only = device_property_present(config->dev, "read-only") |
-			   config->read_only;
+	nvmem->read_only = device_property_present(config->dev, "read-only") ||
+			   config->read_only || !nvmem->reg_write;
 
 	if (config->root_only)
 		nvmem->dev.groups = nvmem->read_only ?