[PATCH 5/7] spl: fit: enable signing a generated u-boot.itb

[Philipp Tomsich]

> On 18.04.2020, at 00:07, Heiko Stuebner <heiko at sntech.de> wrote:
> 
> From: Heiko Stuebner <heiko.stuebner at theobroma-systems.com>
> 
> With SPL_FIT_SIGNATURE enabled we will likely want a generated
> u-boot.itb to be signed and the key stores so that the spl can
> reach it.
> 
> So add a SPL_FIT_SIGNATURE_KEY_DIR option and suitable hooks
> into the Makefile to have mkimage sign the .itb and store the
> used key into the spl dtb file.
> 
> The added dependencies should make sure that the u-boot.itb
> gets generated before the spl-binary gets build, so that there
> is the necessary space for the key to get included.
> 
> Signed-off-by: Heiko Stuebner <heiko.stuebner at theobroma-systems.com>

Reviewed-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>