rtc: struct device - replace bus_id with dev_name(), dev_set_name()

Cc: a.zummo@towertech.it
Cc: rtc-linux@googlegroups.com
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>