readclock: add support for am335x RTC

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
syslib: implement sys_reboot()

Change-Id: Ia604e3d57dbcdc25c96c1aa0a263384982311d09
tps65217: driver for the TPS65217 PMIC

Change-Id: Ic2259c15645816627d757c9c45560cb4c5c0156c
kernel: add support for am335x PMIC-base power-off

AM335X SoCs support power-off via a power management
chip (PMIC). An alarm in the real time clock is used
to trigger the PMIC to cut the power.

To ensure the alarm goes off when the system is in
a safe state, the RTC is frozen when the alarm is
set. At the last moment, the kernel unfreezes the RTC
to let the alarm go off.

This patch adds a mini driver for unfreezing the RTC
as well as code to handle RBT_POWEROFF on Minix/arm.

Change-Id: I7d48e75791e3a81bdd2f7704997193a269409fe8
pm: notify readclock of reboot(RBT_POWEROFF)

Some ARM chips handle power-off with RTC alarms. PM notifies
readclock (the driver for RTCs) about the impending power-off.
If the power-off mechanism is an RTC alarm, readclock will
set the alarm. If not, there is no effect.

Change-Id: Iee00066def2a0f742cdf0dbde8e32b376edf1b78
kernel: implement reboot for am335x/dm37xx

Change-Id: Ied288326b9af8f31223b2dd76a064e32c9a03c45
Importing sys/dev/videomode

NetBSD provides an in-kernel EDID parser, validator, and printer
along with other useful functions. This code will be re-used by
the Minix fb driver as it is a complete and well tested
implementation.

Change-Id: I46fe3005d9957cd90d4972030ddcce7bc3bd7924
fb: auto-configure with EDID

Use EDID when available to configure the frame buffer driver with
good settings for the attached display.

Change-Id: I69a78155a93e55ffa1ca3ff6621a879a56cdbceb
splash: framebuffer test program

Change-Id: I7e045a4c6cec476615057f46f530693c0a2a17e0
splash: use parameters provided by the fb driver

Certain parameters, such as screen resolution, differ between
monitors. Enhance the splash program to dynamically configure
itself.

Change-Id: I49b0a3704decb7cb4633a1ee424b0419a1d67cf0