warp7: hab: Add a CSF location definition

warp7: hab: Add a CSF location definition

In order to correctly produce an image with a IVT/DCD header we need to
define a CSF in imximage.cfg. We just use the mx7 default here.

All we have to do with this option switched on is "make u-boot.imx" and we
then will get

- u-boot.imx
- u-boot.imx.log

The log file is really important because it gives the addresses for the HAB
that we will require to sign the u-boot image using the CST. Since the
addresses can change this logfile is a critical output.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Tested-by: Breno Lima <breno.lima@nxp.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>