thunderbolt: add PCI dependency

The thunderbolt drivers cannot be built if CONFIG_PCI is disabled,
better add an explicit Kconfig dependency.
The "default no" line is redundant and can be removed at the same
time.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Andreas Noever <andreas.noever@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>