ci.yml: Reintroduce build of libscmi-server

A previous patch temporarily removed the libscmi-server build.

Now that the related PR in SCP-firmware has been merged,
reintroduce the build step.

Link: ARM-software/SCP-firmware#812
Link: OP-TEE#6190

Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Etienne Carriere <etienne.carriere@foss.st.com>
Signed-off-by: Nicola Mazzucato <nicola.mazzucato@arm.com>

.github/workflows/ci.yml

@@ -82,8 +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); }
 
-          #Temporarily disabled
-          function download_scp_firmware() { echo "download_scp_firmware skipped"; }
+          function download_scp_firmware() { git clone --single-branch https://github.com/ARM-software/SCP-firmware.git $HOME/scp-firmware || echo Nervermind; }
 
           ccache -s -v
           download_plug_and_trust