power: qpnp-fg-gen4: add support to display available power

Add support to show the available power from battery parameters
through POWER_SUPPLY_PROP_POWER_NOW, POWER_SUPPLY_PROP_POWER_AVG
properties.

Change-Id: Ib13022f0d6acb434190a58e66a502739769322d2
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>