Input: ad7879 - use device core to create driver-specific device attributes

Input: ad7879 - use device core to create driver-specific device attributes

Instead of creating driver-specific device attributes with
devm_device_add_group() have device core do this by setting up dev_groups
pointer in the driver structure.

Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20230729005133.1095051-6-dmitry.torokhov@gmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>