power_supply: Add boot and calibration attributes

Usually PMIC's come with coulomb counting mechanism which can be
used to implement a Fuel Gauginig solution in Software itself.
One of key input to these SW Fuel Gauge solutioons is the boot up
parameters like boot voltage and boot current.

This patch adds the VOLTAGE_BOOT and CURRENT_BOOT power supply attributes
to report bootup voltage and current.

This patch also adds CALIBRATE power supply attribute which useful is
for calibrating the battery/coulomb counter.

Signed-off-by: Ramakrishna Pallala <ramakrishna.pallala@intel.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

Documentation/power/power_supply_class.txt

@@ -101,6 +101,10 @@ VOLTAGE_MAX, VOLTAGE_MIN - same as _DESIGN voltage values except that
 these ones should be used if hardware could only guess (measure and
 retain) the thresholds of a given power supply.
 
+VOLTAGE_BOOT - Reports the voltage measured during boot
+
+CURRENT_BOOT - Reports the current measured during boot
+
 CHARGE_FULL_DESIGN, CHARGE_EMPTY_DESIGN - design charge values, when
 battery considered full/empty.
 
@@ -123,6 +127,8 @@ the current drawn from a charging source.
 CHARGE_TERM_CURRENT - Charge termination current used to detect the end of charge
 condition.
 
+CALIBRATE - battery or coulomb counter calibration status
+
 CONSTANT_CHARGE_VOLTAGE - constant charge voltage programmed by charger.
 CONSTANT_CHARGE_VOLTAGE_MAX - maximum charge voltage supported by the
 power supply object.