arm-bsp/corstone-1000: IMAGE_ROOTFS_EXTRA_SPACE workaround
When images are repacked IMAGE_ROOTFS_EXTRA_SPACE is ignored.
This is not necessarily a bug but an undocumented quirk of how wic
works.
Evaluate IMAGE_ROOTFS_EXTRA_SPACE and use the value with the
--extra-space option. Note that, since IMAGE_ROOTFS_EXTRA_SPACE is in
Kb, the value for `--extra-space` requires the explicit 'K' suffix (the
default is 'M')
Signed-off-by: Adam Johnston <adam.johnston@linaro.org>
Signed-off-by: Jon Mason <jon.mason@arm.com>