rtc: rtc-spear: Provide flag for no support of UIE mode

The applications can set the RTC hardware to trigger interrupts in one
of three modes:
    * AIE: Alarm interrupt
    * UIE: Update interrupt (ie: once per second)
    * PIE: Periodic interrupt (sub-second irqs)

The above defined 3 modes are to be supported in the RTC HW in form of
interrupts. The SPEAr RTC hardware does not support the later two modes.

There have been refinements in the RTC core in mainline related to
use of timer queue infrastructure to manage events in RTC. Please refer
the below mentioned patch for details:
	* RTC: Rework RTC code to use timerqueue for events
	* SHA ID: 6610e089

There have been provisions added to support hardware that do not have
support the UIE mode. Please refer the following patch.
	* rtc: Provide flag for rtc devices that don't support UIE
	* SHA ID: 4a649903



The patch makes use of the provision defined in the above patch to
update the hardware status of UIE mode.

Signed-off-by: Deepak Sikri <deepak.sikri@st.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
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>