thunderbolt: Do not add non-active NVM if NVM upgrade is disabled for retimer

[ Upstream commit ad79c278 ]

This is only used to write a new NVM in order to upgrade the retimer
firmware. It does not make sense to expose it if upgrade is disabled.
This also makes it consistent with the router NVM upgrade.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>