drivers/rtc/rtc-bfin.c: do not abort when requesting irq fails

The RTC framework does not let you return an error once a call to
devm_rtc_device_register has succeeded.  Avoid doing that when the IRQ
request fails as we can still support reading/writing the clock without
the IRQ.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Reported-by: Ales Novak <alnovak@suse.cz>
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>