certs: Add ability to preload revocation certs

Add a new Kconfig option called SYSTEM_REVOCATION_KEYS. If set,
this option should be the filename of a PEM-formated file containing
X.509 certificates to be included in the default blacklist keyring.

DH Changes:
 - Make the new Kconfig option depend on SYSTEM_REVOCATION_LIST.
 - Fix SYSTEM_REVOCATION_KEYS=n, but CONFIG_SYSTEM_REVOCATION_LIST=y[1][2].
 - Use CONFIG_SYSTEM_REVOCATION_LIST for extract-cert[3].
 - Use CONFIG_SYSTEM_REVOCATION_LIST for revocation_certificates.o[3].

Signed-off-by: Eric Snowberg <[email protected]>
Acked-by: Jarkko Sakkinen <[email protected]>
Signed-off-by: David Howells <[email protected]>
cc: Randy Dunlap <[email protected]>
cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]/ [1]
Link: https://lore.kernel.org/r/[email protected]/ [2]
Link: https://lore.kernel.org/r/[email protected]/ [3]
Link: https://lore.kernel.org/r/[email protected]/
Link: https://lore.kernel.org/r/[email protected]/ # v5
Link: https://lore.kernel.org/r/161428673564.677100.4112098280028451629.stgit@warthog.procyon.org.uk/
Link: https://lore.kernel.org/r/161433312452.902181.4146169951896577982.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/161529606657.163428.3340689182456495390.stgit@warthog.procyon.org.uk/ # v3

0 files changed, 0 insertions, 0 deletions