usb: pd: Implement Source_Caps_Extended and Battery messages

For several PD 3.0 Compliance Source tests, if the device is
declared as having a battery, it is required to support the
Source_Capabilities_Extended, Battery_Capabilities and
Battery_Status messages. Add handling for these by reading
from the battery and bms power_supply objects so that these
fields can be populated and returned in response to the
respective Get_* messages.

Change-Id: I3bf1f0ddb1b3fdbacee448f0efed1c3272133b40
Signed-off-by: Jack Pham <jackp@codeaurora.org>