base: soc: populate machine name in soc_device_register if empty

Several SoC drivers use the same of-based mechanism to populate the machine
name. Therefore move this to the core and try to populate the machine name
in soc_device_register if it's not set yet.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Link: https://lore.kernel.org/r/6dbdf458-9f46-613e-de58-b4a56a6cdd9f@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>