add barebox logo ...

in logo/ you will found the barebox logo with color or white
in:
 - png24 (transparent)
 - png8 (black background)

for the following size
 - 100x100
 - 200x200
 - 400x400
 - 600x600
 - 800x800

The logo are origanize in a way to be able to include them in the envfs
by just point as it.

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>