nvmem: core: Return NULL when no nvmem layout is found

Currently, of_nvmem_layout_get_container() returns NULL on error, or an
error pointer if either CONFIG_NVMEM or CONFIG_OF is turned off. We
should likely avoid this kind of mix for two reasons: to clarify the
intend and anyway fix the !CONFIG_OF which will likely always if we use
this helper somewhere else. Let's just return NULL when no layout is
found, we don't need an error value here.

Link: https://staticthinking.wordpress.com/2022/08/01/mixing-error-pointers-and-null/
Fixes: 266570f ("nvmem: core: introduce NVMEM layouts")
Reported-by: kernel test robot <[email protected]>
Reported-by: Dan Carpenter <[email protected]>
Closes: https://lore.kernel.org/r/[email protected]/
Signed-off-by: Miquel Raynal <[email protected]>
Reviewed-by: Michael Walle <[email protected]>
Signed-off-by: Srinivas Kandagatla <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: miquelraynal

include/linux/nvmem-consumer.h

@@ -256,7 +256,7 @@ static inline struct nvmem_device *of_nvmem_device_get(struct device_node *np,
 static inline struct device_node *
 of_nvmem_layout_get_container(struct nvmem_device *nvmem)
 {
-	return ERR_PTR(-EOPNOTSUPP);
+	return NULL;
 }
 #endif /* CONFIG_NVMEM && CONFIG_OF */