scripts: imx: Allow to create signed images ...

This patch allows to call CST directly from imx-image to create signed
images. CST is called whenever the config file contains the hab <str>
commands which means a CSF is generated.
Calling CST requires some quirks. First of all CST returns successfully
whenever a CSF exists, no matter is the CSF actually contains something
sensible or not. So to detect if CST has been called successfully we
have to check if it generated output, not if it returned successfully.
Then CST uses csfsig.bin as a temporary file which breaks when the tool
is called multiple times at once, something which often happens in
parallel builds. We therefore have to lock accesses to this file using
flock().

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

scripts: imx: Create CSF files from imx config file ...

This is the first step to support creating signed images directly
with the imx-image tool. i.MX images must be signed using the Freescale
CST tool. CST needs informations already present in the imx-image tool,
so it's convenient to call CST directly from imx-image.
CST takes CSF files (Command Sequence Files) as input. This patch
supports generating CSF files from the imx-image configuration file.
This adds three new commands to the config file:

hab <str>:  All options to the hab command are directly passed through to
            the CSF.
hab_blocks: This generates the "Blocks =" line in the CSF. This is the
            place where the CSF needs information which is contained in
	    the imx-image tool: The image size, the image filename and
	    the load address.
super_root_key <file>: For HABv3 the super root key hash is needed in
                       the i.MX flash header. This command is used to
		       specify the path to the super root key. Needed
		       for HABv3 only.

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

scripts: imx: Drop double check ...

We have the same "if (*line == '\0')" check twice. Remove one of them.

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

scripts: imx: move config file parser to separate file ...

To make the config parser usable by imx-usb-loader also move
it to a separate file.

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