Do not display USB charging dialogue for AUDIO class devices

The CL prevents the "Supplying power to the attached device"
notification from showing up when USB digital headphones are
connected. Although, the phone is actually powering the headphones
here, there seems to be an opinion that this might confuse the users.
So, disabling the notification for better user experience.

Also, the mode chooser activity might not be applicable here as
the headphones are not expected to be a dual role device in the
near future. When connected through a hub, the power management
of the Type-c link is expected to be managed by the Type-C stack
in the hub and phone's kernel. So user might not have to manage
the direction of power flow.

Bug: 36141499
Test: Manually tested that USB dialog doesnt show up when
digital usb headphones are connected but shows up otherwise.
Change-Id: I187da9c77e294cbbceb633365adbb4623fc14a3d