drivers/rtc/class.c: initialize rtc name early

In some error cases RTC name is used before it is initialized:

	rtc-rs5c372 0-0032: clock needs to be set
	rtc-rs5c372 0-0032: rs5c372b found, 24hr, driver version 0.6
	rtc (null): read_time: fail to read
	rtc-rs5c372 0-0032: rtc core: registered rtc-rs5c372 as rtc0

Fix by initializing the name early.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>