util/docker: Minor Makefile updates

- Update url for docker install instructions.
- Update docker-cleanall target to require verification.
- Update docker-jenkins-attach target to check for docker and
use docker variable.
- Update spaces to tabs in the docs targets.

Signed-off-by: Martin Roth <martin@coreboot.org>
Change-Id: Ic1e1a545024fe1fdc37d7d8c7e6f54f124d1697b
Reviewed-on: https://review.coreboot.org/c/coreboot/+/47342
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

0 files changed, 0 insertions, 0 deletions