rtc: Cleanup removed UIE emulation declaration

rtc_dev_update_irq_enable_emul was removed in commit
042620a018afcfba1d678062b62e463b9e43a68d (UIE emulation is
now handled via hrtimer), but the declaration was missed.
This patch cleans it up.

Signed-off-by: John Stultz <john.stultz@linaro.org>
LKML-Reference: <1294939849-20608-1-git-send-email-john.stultz@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>