Add two additional attributes to the existing power participant driver:
rest_of_platform_power_mw: (RO) Shows the rest of worst case platform
power in mW outside of S0C. This will help in power distribution to SoC
and rest of the system. For example on a test system, this value is 2.5W
with a 15W TDP SoC. Based on the adapter rating (adapter_rating_mw), user
space software can decide on proper power allocation to SoC to improve
short term performance via powercap/RAPL interface.

prochot_confirm: (WO) Confirm EC about a prochot notification.

Also userspace is notified via sysfs_notify(), whenever power source or
rest of the platform power is changed. So user space can use poll()
system call on those attributes.

The ACPI methods used in this patch are as follows:

PROP
This object evaluates to the rest of worst case platform power in mW.
Bits:
23:0 Worst case rest of platform power in mW.

PBOK
PBOK is a method designed to provide a mechanism for OSPM to change power
setting before EC can de-assert a PROCHOT from a device. The EC may
receive several PROCHOTs, so it has a sequence number attached to PSRC
(read via existing attribute "platform_power_source"). Once OSPM takes
action for a PSRC change notification, it can call PBOK method to confirm
with the sequence number.
Bits:
3:0 Power Delivery State Change Sequence number
30  Reserved
31  0 – Not OK to de-assert PROCHOT
    1 – OK to de-assert PROCHOT

PSRC (Platform Power Source): Not new in this patch but for
documentation for new bits
This object evaluates to an integer that represents the system power
source as well as the power delivery state change sequence number.
Bits:
3:0 The current power source as an integer for AC, DC, USB, Wireless.
0 = DC, 1 = AC, 2 = USB, 3 = Wireless Charging
7:4 Power Delivery State Change Sequence Number. Default value is 0

Notifications:
0x81: (Power State Change) Used to notify when the power source has
changed.
0x84: (PROP change) Used to notify when the platform rest of power has
changed.
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
[ rjw: Subject, minor ABI documentation edit ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>