tf-sync-github-repos: update Gerrit URLs of crates

Crates which used to live under the rust-spmc/ namespace have now moved
under the arm-firmware-crates/ namespace.

Reflect this in the sync script so the mirroring from tf.org Gerrit to
Github keeps working.

Change-Id: Iaa4ef047927bb201ce9249c274616161b758211b
Co-authored-by: Balint Dobszay <balint.dobszay@arm.com>
Signed-off-by: Sandrine Afsa <sandrine.afsa@arm.com>
2 files changed