gemini: switch to 4.14

gemini: switch to 4.14

This introduces Device/ infrastructure and images
for all boards available upstream.

Changes from Linus submitted version:
- fix Raidsonic image generation
- remove redundant (old) image generation
- remove redundant header tool for dns313 board

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Roman Yeryomin <roman@advem.lv>