thunderbolt: Prevent root port runtime suspend during NVM upgrade

During NVM upgrade process the host router is hot-removed for a short
while. During this time it is possible that the root port is moved into
D3cold which would be fine if the root port could trigger PME on itself.
However, many systems actually do not implement it so what happens is
that the root port goes into D3cold and never wakes up unless userspace
does PCI config space access, such as running 'lscpi'.

For this reason we explicitly prevent the root port from runtime
suspending during NVM upgrade.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>