vboot: various Makefile cleanups
vboot: various Makefile cleanups

- Lists should be alphabetically sorted
- No need for CHROMEOS_ENVIRONMENT variable
- Remove some defunct sections
- Merge VBINIT and VBSLK into FWLIB

BUG=b:124141368
TEST=make clean && make runtests
BRANCH=none

Change-Id: Id05508a8be6273f11c1886fd9a35d30be4bb778f
Signed-off-by: Joel Kitching <c2feea8c1334a0d339e816ae4c7c9ecfa9b30a91@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/1773087
Reviewed-by: Joel Kitching <c2feea8c1334a0d339e816ae4c7c9ecfa9b30a91@chromium.org>
Commit-Queue: Joel Kitching <c2feea8c1334a0d339e816ae4c7c9ecfa9b30a91@chromium.org>
Tested-by: Joel Kitching <c2feea8c1334a0d339e816ae4c7c9ecfa9b30a91@chromium.org>

coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot