rtc/pxa: remove unnecessary private ops->ioctl()

We shouldn't implement private ops->ioctl() unless absolutely necessary.
pxa series RTC driver's ioctl() is unnecessary, since RTC subsystem has
implement the ioctl() very well,so we can only use the API of
'.alarm_irq_enable' and '.update_irq_enable' to do enable irq action.

Signed-off-by: Wan ZongShun <mcuos.com@gmail.com>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Acked-by: Eric Miao <eric.y.miao@gmail.com>
Cc: Paul Gortmaker <p_gortmaker@yahoo.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>