driver core: move sysfs_dev_char_kobj out of class.h

The structure sysfs_dev_char_kobj is local only to the driver core code,
so move it out of the global class.h file and into the internal base.h
file as no one else should be touching this symbol.

Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/20230327160319.513974-1-gregkh@linuxfoundation.org


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