staging: greybus: auto_manager: use default_groups in kobj_type

staging: greybus: auto_manager: use default_groups in kobj_type

There are currently 2 ways to create a set of sysfs files for a
kobj_type, through the default_attrs field, and the default_groups
field.  Move the greybus audio code to use default_groups field which
has been the preferred way since aa30f47cf666 ("kobject: Add support for
default attribute groups to kobj_type") so that we can soon get rid of
the obsolete default_attrs field.

Cc: Vaibhav Agarwal <vaibhav.sr@gmail.com>
Cc: Johan Hovold <johan@kernel.org>
Reviewed-by: Alex Elder <elder@linaro.org>
Acked-by: Mark Greer <mgreer@animalcreek.com>
Link: https://lore.kernel.org/r/20211228135541.380275-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>