staging: most: dim2: do not double-register the same device

Commit 723de0f9 ("staging: most: remove device from interface
structure") moved registration of driver-provided struct device to
the most subsystem.

Dim2 used to register the same struct device to provide a custom device
attribute. This causes double-registration of the same struct device.

Fix that by moving the custom attribute to driver's dev_groups.
This moves attribute to the platform_device object, which is a better
location for platform-specific attributes anyway.

Fixes: 723de0f9

 ("staging: most: remove device from interface structure")
Acked-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Link: https://lore.kernel.org/r/20211011061117.21435-1-nikita.yoush@cogentembedded.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>