thunderbolt: Add tb_regs.h

Every thunderbolt device consists (logically) of a switch with multiple
ports. Every port contains up to four config regions (HOPS, PORT,
SWITCH, COUNTERS) which are used to configure the device.

The tb_regs.h file contains all known registers and capabilities from
these config regions.

Signed-off-by: Andreas Noever <andreas.noever@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>