nvmem: core: let stride and word_size default to 1

If the caller doesn't set stride and/or word_size in struct nvmem_config
then nvmem_register accepts this but we may face strange effects later
due to both values being 0. Therefore use 1 as default for both values.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>