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>

drivers/thunderbolt/Kconfig

 menuconfig THUNDERBOLT
 	tristate "Thunderbolt support for Apple devices"
-	default no
+	depends on PCI
 	help
 	  Cactus Ridge Thunderbolt Controller driver
 	  This driver is required if you want to hotplug Thunderbolt devices on