CHANGELOG.md: Update for IMAGE_ROOTFS_MAXSIZE calculation
CHANGELOG.md: Update for IMAGE_ROOTFS_MAXSIZE calculation

Signed-off-by: Will Newton <9ae5e71ad61fb3eb3f972773b758e0d4f6c5e573@resin.io>

resin-os/meta-resin,resin-os/meta-resin,resin-os/meta-resin,resin-os/meta-resin