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>
diff --git a/arch/arm/mach-alpine/Makefile b/arch/arm/mach-alpine/Makefile
index b667489..acbe013 100644
--- a/arch/arm/mach-alpine/Makefile
+++ b/arch/arm/mach-alpine/Makefile
@@ -1,2 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
 obj-y				+= alpine_machine.o
 obj-$(CONFIG_SMP)		+= platsmp.o alpine_cpu_pm.o