u-boot-tools: Support FIT image creation
u-boot-tools: Support FIT image creation

Re-apply the addition of FIT image support.  It was added in PR #43 and
silently dropped in PR #244.

Signed-off-by: Esben Haabendal <da90c138e4a9573086862393cde34fa33d74f6e5@haabendal.dk>
(cherry picked from commit 00e1ff920644bec4ffe2222c5cd045ccc7212370)

esben/base,moths/base,oe-lite/base,esben/base,esben/base,oe-lite/base,esben/base,moths/base,oe-lite/base,oe-lite/base,moths/base,moths/base,esben/base,moths/base,oe-lite/base,esben/base,moths/base,oe-lite/base