redhat/configs: automotive: enable extra system cert

JIRA: https://issues.redhat.com/browse/RHEL-78808

Upstream Status: https://gitlab.com/cki-project/kernel-ark.git

commit 4eb9bfe078b6ee95bfdfe8e1acd309b441a927f1
Author: Eric Chanudet <echanude@redhat.com>
Date:   Fri Jun 27 16:35:34 2025 -0400

    redhat/configs: automotive: enable extra system cert

    Reserve an area in the certificate ring to add another one without
    recompiling. Arbitrarily choose 4k, but odds are this can be lowered.

    This is intended to be used in the automotive images where the modules
    are signed when the image is composed instead of when the kernel and
    modules are built.

    Signed-off-by: Eric Chanudet <echanude@redhat.com>

Signed-off-by: Eric Chanudet <echanude@redhat.com>

Author: eric-ch

redhat/configs/rhel/automotive/generic/CONFIG_SYSTEM_EXTRA_CERTIFICATE

@@ -0,0 +1 @@
+CONFIG_SYSTEM_EXTRA_CERTIFICATE=y

redhat/configs/rhel/automotive/generic/CONFIG_SYSTEM_EXTRA_CERTIFICATE_SIZE

@@ -0,0 +1 @@
+CONFIG_SYSTEM_EXTRA_CERTIFICATE_SIZE=4096