treewide: Add SPDX license identifier - Makefile/Kconfig

Add SPDX license identifiers to all Make/Kconfig files which:

- Have no license information of any form

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

GPL-2.0-only

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

r6040: Move the RDC driver

Move the RDC driver into drivers/net/ethernet/rdc/ and make the
necessary Kconfig and Makefile changes.

CC: Florian Fainelli <florian@openwrt.org>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>