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>

[ALSA] Emagic Audiowerk 2 ALSA driver.

Signed-off-by: Cedric Bregardis <cedric.bregardis@free.fr>
Signed-off-by: Jean-Christian Hassler <jhassler@free.fr>
Signed-off-by: Takashi Iwai <tiwai@suse.de>