ci: sync SCP-firmware on v2.13.0 release tag

Synchronize SCP-firmware Git repository revision on v2.13.0 release
tag to avoid issues with latest merged changes in SCP-firmware that
OP-TEE OS may not be compliant with.

Signed-off-by: Etienne Carriere <etienne.carriere@foss.st.com>

.github/workflows/ci.yml

@@ -82,7 +82,7 @@ jobs:
           function _make() { make -j$(nproc) -s O=out $*; }
           function download_plug_and_trust() { mkdir -p $HOME/se050 && git clone --single-branch -b v0.4.2 https://github.com/foundriesio/plug-and-trust $HOME/se050/plug-and-trust || (rm -rf $HOME/se050 ; echo Nervermind); }
 
-          function download_scp_firmware() { git clone --single-branch https://github.com/ARM-software/SCP-firmware.git $HOME/scp-firmware || echo Nervermind; }
+          function download_scp_firmware() { { git clone --single-branch https://github.com/ARM-software/SCP-firmware.git $HOME/scp-firmware && git checkout v2.13.0; } || echo Nervermind; }
 
           ccache -s -v
           download_plug_and_trust