documentation: Add small coreboot logo in PNG format

The doxygen output looks better with the coreboot logo,
so I'm adding the 2k png from the wiki to the documentation
directory to use in the doxygen build.

Change-Id: I95ca67fb311e0b39a12ad9c5a1a53a99f7fec2d9
Signed-off-by: Martin Roth <martin.roth@se-eng.com>
Reviewed-on: http://review.coreboot.org/8067
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Tested-by: build bot (Jenkins)
1 file changed