rtc: mc13xxx: request IRQs after RTC registration

Interrupts can appear after request_irq and interrupt handlers can use
the RTC device, but currently we register RTC after IRQs.  This patch
changes this order and simplify error path a bit.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Sascha Hauer <kernel@pengutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>