bootm: Split bootm_load_devicetree into two functions ...

It is not always desired to get the devicetree from image data and load
it to a SDRAM region at the same time. Sometimes it's enough to just
load it to an allocated address (in case the user has no constraints
where the devicetree should be placed.

This patch splits bootm_load_devicetree into bootm_get_devicetree which
returns a pointer to the allocated devicetree and bootm_load_devicetree
which loads the devicetree to a specified region.

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

bootm: Drop data->oftree ...

It's no longer necessary to store the devicetree pointer in struct
image_data, it can be replaced with a local variable.

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

bootm: provide handlers the start of the OS image ...

The bootm code needs to read the beginning of the OS image in order to
determine the filetype. If it does so already, then we can provide the
handlers the buffer. This can help the handlers to find some image
metadata before loading the full image.

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>

bootm: FIT: do not depend on FIT pre-opened images ...

When calling fit_open_configuration the FIT code already opens
the images "kernel", "ramdisk" and "dtb". This does not fit well
into the FIT code, so make the bootm code independent of these
pre-opened images so that we can drop the opening from the FIT
code in the next step.

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>