mISDN: remove unneeded mISDN_class_release()

mISDN: remove unneeded mISDN_class_release()

The mISDN_class_release() is not needed at all, as the class structure
is static, and it does not actually do anything either, so it is safe to
remove as struct class does not require a release callback.

Cc: Karsten Keil <isdn@linux-pingi.de>
Cc: netdev@vger.kernel.org
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20230329060127.2688492-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>