bsp: Align Corstone-1000 image configuration with mender

Aligns mender related configuration for Corstone-1000 platform.
Additionally, Corstone-1000 capsule key and certificate files are
already installed by u-boot recipe and mender build triggers
firmware-deploy task again to copy these binaries which causes an
issue. So this commits also removes capsule key and certification for
Corstone-1000 for mender builds.

Signed-off-by: Vikas Katariya <vikas.katariya@arm.com>
Signed-off-by: Emekcan Aras <Emekcan.Aras@arm.com>