thunderbolt: Update Kconfig entries to USB4

thunderbolt: Update Kconfig entries to USB4

Since the driver now supports USB4 which is the standard going forward,
update the Kconfig entry to mention this and rename the entry from
CONFIG_THUNDERBOLT to CONFIG_USB4 instead to help people to find the
correct option if they want to enable USB4.

Also do the same for Thunderbolt network driver.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: David S. Miller <davem@davemloft.net>
Link: https://lore.kernel.org/r/20191217123345.31850-6-mika.westerberg@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>