[U-Boot] Logo for U-Boot

[Heinrich Schuchardt]

U-Boot has currently no logo that we can use in presentations.

On the U-Boot IRC channel the following propositions where made:

Source: https://commons.wikimedia.org/wiki/File:Circle-icons-submarine.svg
License: GPL2+
(Alex used this in some presentations.)

Source: https://gist.github.com/xypron/a923ad8cca83e648fc91716f2f29beed
License: GPL2+
(The image is already used in U-Boot:
setenv efi_selftest block image transfer
bootefi selftest
)

Looking forward to your further suggestions.

Best regards

Heinrich