mtd: mtdpart: Don't create platform device that'll never probe

These "nvmem-cells" platform devices never get probed because there's no
platform driver for it and it's never used anywhere else. So it's a
waste of memory. These devices also cause fw_devlink to block nvmem
consumers of "nvmem-cells" partition from probing because the supplier
device never probes.

So stop creating platform devices for nvmem-cells partitions to avoid
wasting memory and to avoid blocking probing of consumers.

Reported-by: Maxim Kiselev <bigunclemax@gmail.com>
Fixes: bcdf0315

 ("mtd: call of_platform_populate() for MTD partitions")
Signed-off-by: Saravana Kannan <saravanak@google.com>
Tested-by: Maksim Kiselev <bigunclemax@gmail.com>
Tested-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Luca Weiss <luca.weiss@fairphone.com> # qcom/sm7225-fairphone-fp4
Link: https://lore.kernel.org/r/20230207014207.1678715-13-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>