Add a debug register

Add a debug register

This patch uses the possibility to add a vendor-specific register and
adds a debug register useful for dumping the TIS's internal state. This
register is only active in a debug build (#define DEBUG_TIS).

Signed-off-by: Stefan Berger <[email protected]>
Reviewed-by: Corey Bryant <[email protected]>
Reviewed-by: Joel Schopp <[email protected]>
Message-id: 1361987275[email protected]
Signed-off-by: Anthony Liguori <[email protected]>