Provide the possibility to allow users to synchronize
the RTC. It is (still) disabled by default, since
certain combinations of linux kernel version and
hardware pieces are subject to cause lockups.
"rtcautotrim 10" and rtcfile have been favoured over
"rtcsync" since "rtcsync" syncs the RTC every 11 seconds
which is not necessary IMO. "rtcautotrim 10" will only
set the time to the RTC if the gap between RTC and
the system clock exceed more than 10 seconds.
Change-Id: I2961bc554eb6caf6e6c78137a33c4fde256ae1ff
06f05b2984