Add support for getting/setting the am335x SoC's internal real
time clock. Also, allow the power off alarm to be set.
Make readclock an "always on" driver. This is needed for setting
power-off alarms whenever the power button is pressed on the BBB.
Replace the readclock.sh script & single run driver with a
readclock program that takes the same arguments and forwards
the requests on to the always up readclock driver.
Change-Id: Ifd6c2acd80ae4b5e79d83df510df445c24e24a71
