DFU TEST CASE DESCRIPTION:

The prerequisites for running this script are assured by dfu_gadget_test_init.sh.
In this file user is able to generate their own set of test files by altering
the default set of TEST_FILES_SIZES variable.
The dfu_gadget_test_init.sh would generate test images only if they are not
already generated.

Moreover, on a target device the "dfu_alt_info" env variable should be extended
to have "dfu_test.bin fat 0 6;" \ entry ([1]). For reference please consult the
config file for TRATS/TRATS2 devices (./include/configs/trats{2}.h)

One can use fat, ext4 or any other supported file system, which can be
created in a convenient way with exporting partitions via UMS (ums 0 mmc 0)
and using standard tools on host (like mkfs.ext4).

Example usage:
1. On the target:
   env default -a
   dfu 0 mmc 0
2. On the host:
   ./dfu_gadget_test.sh 11 [test_file]

where 11 is the mumber of alt setting corresponding to entry [1] and [test_file]
is an optional parameter, with which one can explicitly indicate the test file
to be used.

The number of the alt setting entry can be obtained with dfu-util -l command.
In its output one should look for the 'name="dfu_test1.bin"' and corresponding
alt=11.