am62x: Add core-secdev-k3 from non-free

We need access to custMpk.pem to build the HS-FS boot firmware. This is currently failing in CI and as of v2025dev1 is being detected as a failure:

2023/12/05 02:05:44 ==== Assemble and sign HS-FS R5 boot firmware ====
7552023/12/05 02:05:44 ${ROOTDIR}/usr/lib/k3-image-gen/scripts/... | Certificate being generated :
7562023/12/05 02:05:44 ${ROOTDIR}/usr/lib/k3-image-gen/scripts/... |  private key from /scratch/mnt/usr/lib/core-secdev-k3/keys/custMpk.pem
7572023/12/05 02:05:44 ${ROOTDIR}/usr/lib/k3-image-gen/scripts/... | 40A73E38077F0000:error:16000069:STORE routines:ossl_store_get0_loader_int:unregistered scheme:../crypto/store/store_register.c:237:scheme=file
7582023/12/05 02:05:44 ${ROOTDIR}/usr/lib/k3-image-gen/scripts/... | 40A73E38077F0000:error:80000002:system library:file_open:No such file or directory:../providers/implementations/storemgmt/file_store.c:267:calling stat(/scratch/mnt/usr/lib/core-secdev-k3/keys/custMpk.pem)
7592023/12/05 02:05:44 ${ROOTDIR}/usr/lib/k3-image-gen/scripts/... | cat: certificate.bin: No such file or directory
7602023/12/05 02:05:44 ${ROOTDIR}/usr/lib/k3-image-gen/scripts/... | SUCCESS: Image /scratch/mnt/usr/lib/k3-image-gen/tiboot3-am62x-hs-fs-evm.bin generated.
7612023/12/05 02:05:44 ${ROOTDIR}/usr/lib/k3-image-gen/scripts/... | rm: cannot remove 'certificate.bin': No such file or directory

It's not ideal, but install the package into the image for now so as to enable images to be built. Ideally we wouldn't be installing this or the other dependencies for generating the boot firmware into the image. Task apertis-issues#491 created to look into improving this situation.

Signed-off-by: Martyn Welch martyn.welch@collabora.com