siemens: capricorn: move to cxg3 reference project with deneb board

We have many HW with capricorn i.MX8X boards. The difference in u-boot is
at all by the display of the LEDs.

* put upstream a reference project & board for DT and defconfig
* use the capricorn prefix outside the board/siemens/capricorn folder

Signed-off-by: Enrico Leto <enrico.leto@siemens.com>
Signed-off-by: Heiko Schocher <hs@denx.de>
11 files changed