thunderbolt: Move constants for USB4 router operations to tb_regs.h

commit 579f1421 upstream.

We are going to use these in subsequent patch so make them available
outside of usb4.c.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Liwei Song <liwei.song@windriver.com>