usb: dfu: Add support for alternate settings

Add support for alternate settings in order to access additional flash areas.
The DFU example uses the alternate settings as an offset into flash.

Change-Id: I636042c7f71a5d2a2778ec7dd5301a622720107d
Signed-off-by: Adrian Bradianu <adrian.bradianu@windriver.com>
2 files changed