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>

tools: usb: aio example applications

This patch adds two example applications showing usage of Asynchronous I/O API
of FunctionFS. First one (aio_simple) is simple example of bidirectional data
transfer. Second one (aio_multibuff) shows multi-buffer data transfer, which
may to be used in high performance applications.

Both examples contains userspace applications for device and for host.
It needs libaio library on the device, and libusb library on host.

Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>