usb: pd: Add missing 'break' when handling VCONN_Swap

The switch case for handling VCONN_Swap within SNK_Ready state
was missing a 'break' statement, which allows the control flow
to inadvertently fall through the Get_Source_Caps_Extended
handling and causes an unexpected Source_Capabilities_Extended
message to get sent out. This could lead to the port partner
responding with a Not_Supported or worse, cause a soft/hard reset.

Change-Id: I6919c33bc2c89b08f605cb2c44c699a76402e112
Signed-off-by: Jack Pham <jackp@codeaurora.org>