nvmem: core: Allow allocating several anonymous nvmem devices

nvmem: core: Allow allocating several anonymous nvmem devices

Currently the nvmem core expect the config to provide a name and ID
that are then used to create the device name. When no device name is
given 'nvmem' is used. However if there is several such anonymous
devices they all get named 'nvmem0', which doesn't work.

To fix this problem use the ID from the config only when the config
also provides a name. When no name is provided take the uinque ID of
the nvmem device instead.

Signed-off-by: Aban Bedel <albeu@free.fr>
Reviewed-by: Moritz Fischer <mdf@kernel.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>