thunderbolt: Use constants for path weight and priority

[ Upstream commit f73edddf ]

Makes it easier to follow and update. No functional changes.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Qin Wan <qin.wan@hp.com>
Signed-off-by: Alexandru Gagniuc <alexandru.gagniuc@hp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>