Convert these to rST format and add them to the index.

Signed-off-by: Simon Glass <sjg@chromium.org>

This patch adds an example FIT image description file demonstrating
the usage of bootm command to securely launch UEFI binaries.

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>