qcom-charger: smb2: fix kernel log flooding by charger driver

Power supply framework expects all registered power_supply
entities(except "battery" psy) to support ONLINE property.
"usb-main" psy doesn't support ONLINE property and prints
error for unsupported properties in get_property function.
Update error prints to debug in get-property function of
"usb-main" to prevent log flooding.

Change-Id: I270a93fe2e48d368f13e74e63c48613c1a4fb693
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>