Use environment variable for download server

To ensure tf-a-ci-scripts can run on both OpenCI
and Arm CI, replace ci.trustedfirmware.org with
enironment variable.

DOWNLOAD_SERVER_URL is a system-wide environment
variable and was configured in:
Manage Jenkins > System > Global Properties

Change-Id: I12b6fe570046accce064a6ed06e42846093630aa
Signed-off-by: Saheer Babu <saheer.babu@arm.com>
diff --git a/openci-env.sh b/openci-env.sh
index f96f584..797230c 100644
--- a/openci-env.sh
+++ b/openci-env.sh
@@ -11,4 +11,4 @@
 
 nfs_volume="${WORKSPACE:?}/nfs"
 jenkins_url="http://ci.trustedfirmware.org"
-tfa_downloads="https://downloads.trustedfirmware.org/tf-a"
+tfa_downloads="${DOWNLOAD_SERVER_URL}/tf-a"
diff --git a/openci-lts-v2.8-env.sh b/openci-lts-v2.8-env.sh
index 58e14ed..2b0269c 100644
--- a/openci-lts-v2.8-env.sh
+++ b/openci-lts-v2.8-env.sh
@@ -11,4 +11,4 @@
 
 nfs_volume="${WORKSPACE:?}/nfs"
 jenkins_url="http://ci.trustedfirmware.org"
-tfa_downloads="https://downloads.trustedfirmware.org/tf-a-lts-v2.8"
+tfa_downloads="${DOWNLOAD_SERVER_URL}/tf-a-lts-v2.8"
diff --git a/openci-staging-env.sh b/openci-staging-env.sh
index d975da4..6904cff 100644
--- a/openci-staging-env.sh
+++ b/openci-staging-env.sh
@@ -11,4 +11,4 @@
 
 nfs_volume="${WORKSPACE:?}/nfs"
 jenkins_url="http://ci.staging.trustedfirmware.org"
-tfa_downloads="https://downloads.trustedfirmware.org/tf-a"
+tfa_downloads="${DOWNLOAD_SERVER_URL}/tf-a"
diff --git a/script/tf-coverity/tf-cov-make b/script/tf-coverity/tf-cov-make
index 6fa777f..87ed27c 100755
--- a/script/tf-coverity/tf-cov-make
+++ b/script/tf-coverity/tf-cov-make
@@ -484,7 +484,7 @@
 
 # Source files from mv-ddr-marvell repository are necessary
 # to build below four platforms
-wget https://downloads.trustedfirmware.org/tf-a/mv-ddr-marvell/mv-ddr-marvell-5d41a995637de1dbc93f193db6ef0c8954cab316.tar.gz 2> /dev/null
+wget ${DOWNLOAD_SERVER_URL}/tf-a/mv-ddr-marvell/mv-ddr-marvell-5d41a995637de1dbc93f193db6ef0c8954cab316.tar.gz 2> /dev/null
 tar -xzf mv-ddr-marvell-5d41a995637de1dbc93f193db6ef0c8954cab316.tar.gz 2> /dev/null
 mv mv-ddr-marvell drivers/marvell/mv_ddr