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>

drivers/media/common/saa7146/Kconfig

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
 config VIDEO_SAA7146
 	tristate
 	depends on I2C && PCI

drivers/media/common/saa7146/Makefile

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
 saa7146-objs    := saa7146_i2c.o saa7146_core.o
 saa7146_vv-objs := saa7146_fops.o saa7146_video.o saa7146_hlp.o saa7146_vbi.o