FIT: Allow to open buffer as FIT image ...

This adds fit_open_buf() which can open a buffer as FIT image.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

FIT: store device_nodes in fit_handle ...

We need the /images and /configurations nodes more than once,
so store them in the fit_handle rather than searching for them
each time again.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

FIT: Let user specify the configuration to use ...

The images in FIT images can be opened in two different ways. They
can be either opened directly based on their names in the images/
node or as part of a configuration based on their names in the
corresponding /configuration/ node.

So far we only supported the latter. To prepare supporting the former
we return a cookie belonging to the configuration from
fit_open_configuration() which we use in fit_open_image() to refer
to the desired configuration.

While at it document fit_open_configuration().

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

FIT: Do not pre-open images ...

Only do what fit_open_configuration() suggests: open the configuration,
but not the images in it.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

FIT: export fit_open_configuration() and fit_open_image() ...

Currently only fit_open() is exported which only opens the predefined
images "kernel", "dtb" and "ramdisk". To make the FIT code more usable
for other code which may want to open other images export
fit_open_configuration() and fit_open_image().

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

include: Move bulk of boot.h to bootm.h ...

The majority of the stuff currently in include/boot.h is about bootm
code implemented common/bootm.c. To be more consistent move it to a
new file include/bootm.h.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

bootm: add initial FIT support ...

This implementation is inspired by U-Boot's FIT support. Instead of
using libfdt (which does not exist in barebox), configuration signatures
are verified by using a simplified DT parser based on barebox's own
code.

Currently, only signed configurations with hashed images are supported,
as the other variants are less useful for verified boot. Compatible FIT
images can be created using U-Boot's mkimage tool.

Signed-off-by: Jan Luebbe <jlu@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>