usb: pd: Add support to send PD 3.0 extended messages

Add support for sending extended messages. Since the underlying
PD PHY only supports a fixed 30 byte payload, longer messages up
to 260 bytes must use chunking, which requires the receiver to
request the next chunk until the entire payload is delivered.
Use a completion variable to wait for the chunk requests so that
pd_send_ext_msg() can be a blocking call. Send following two
extended messages using sysfs in SINK ready state and cache response:-

1) Get_Battery_Cap and Battery_Capabilities as response
2) Get_Battery_Status and Battery_Status as response.

These two extended messages are recommended for PD 3.0 SINK.

Change-Id: Ib2b4e658c47995de1ea139406d7d83737c6208d4
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>