coresight: tmc: Add usb support for coresight

Add support to enable USB mode for coresight devices.
Set memory as the default mode on ETR.

Change-Id: Id804fb819ad19b589a1b978ea0cd65b0265a9268
Signed-off-by: Satyajit Desai <sadesai@codeaurora.org>
Signed-off-by: Rama Aparna Mallavarapu <aparnam@codeaurora.org>