DT binding allows specifying NVMEM cells as NVMEM device (provider)
subnodes. Looks for such subnodes when building NVMEM cells.

This allows NVMEM consumers to use U-Boot environment variables.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20220916122100.170016-11-srinivas.kandagatla@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>