ARM: add auto hotplug driver
Motley's auto_hotplug enhancements (rebased)

auto_hotplug: rev 4 - let's lean a little more towards performance.

This includes:

1) Set DEFAULT_SAMPLING_PERIODS back to 10 (from 12)

2) Set DEFAULT_ENABLE_ALL_LOAD_THRESHOLD to (100 * CPUS)

3) Finally came back and fixed "stack the deck" like I had originally
intended after the quick test.

4) Updated to revision to 4.
auto_hotplug: stack the deck on auto_hotplug_late_resume to get things
moving quickly again
auto_hotplug: parameter validation for max_online_cpus

If validation fails, set max_online_cpus = CPUS_AVAILABLE instead of
"1"
auto_hotplug: enhancements (rev 3)

1) Added max_online_cpus (1-4) and exposed to sysfs via a module
parameter. Once set, only allow the chosen number of cores to be
online and make sure we compensate for it in the boostpulse function.

2) Make minor tweaks to mathkid's min_online_cpus

-Don't schedule work in the parameter set, just let it be done on the
next poll iteration.

-Misc style changes so that it matches the other code I have been
adding the module.
auto_hotplug: enable the min_online_cpus value

Use a module_param_cb to set the minimum number of online CPUs when the
screen is on.

The values are between 1-4.

usage:
echo '1' < /sys/module/auto_hotplug/parameters/min_online_cpus
auto_hotplug: enhancements (rev 2)

1) Added ability to change the number of sampling_periods on the fly via
sysfs (while preserving past history).

2) Added get/set for module parameters so user's can't set incorrect or
unreasonable values.

3) Tweaked defaults

4) Don't wait as long to start auto_hotplug (referenced franco's
git). Today's devices are much faster to boot however
if this code is ported to a slower core device, it may need to be
raised.

5) Debug mode tweaks
-Organize and reduce the number of line output.
-Attempt to make output more user friendly for those that aren't
reading the code.
auto_hotplug: enhancements

1) added module params so tuning an be adjusted in userspace and
debugging can easliy be enabled/disabled

/sys/module/auto_hotplug/parameters/debug
(N/Y - turn off/on debugging)

/sys/module/auto_hotplug/parameters/disable_load_threshold
(integer - load at which a CPU is disabled)

/sys/module/auto_hotplug/parameters/enable_load_threshold (integer -
load at which an extra CPU is enabled)

/sys/module/auto_hotplug/parameters/enable_all_load_threshold (integer -
load at wich all CPU's are enabled)

/sys/module/auto_hotplug/parameters/min_sampling_rate
(milliseconds, converted to jiffies at runtime)

2) lowered enable_load_threshold from 225 to 200 for a little more pep.

To-do: add get/set routines to keep values safe and in acceptable ranges
arm: auto hotplug - wrap all pr_info into the existing debug mode so we
don't spam the kernel log