byteorder: Move {cpu_to_be32, be32_to_cpu}_array() from Thunderbolt to core

We will be using these when communicating XDomain discovery protocol
over Thunderbolt link but they might be useful for other drivers as
well.

Make them available through byteorder/generic.h.

Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Michael Jamet <michael.jamet@intel.com>
Reviewed-by: Yehezkel Bernat <yehezkel.bernat@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>