Migrate support to MbedTLS v2.26.0

Updated CI scripts to use latest release tagged MbedTLS repo
i.e. MbedTLS v2.26.0.

Release notes of Mbed TLSv2.26.0 are available here:
https://github.com/ARMmbed/mbedtls/releases/tag/v2.26.0

Change-Id: Ide402d96c717f7259168b1d5d3c0d2630a228a80
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
diff --git a/arm-env.sh b/arm-env.sh
index a8e7c5a..9d80736 100644
--- a/arm-env.sh
+++ b/arm-env.sh
@@ -25,7 +25,7 @@
 tf_for_scp_tools_src_repo_url="https://gerrit.oss.arm.com/scp/test-framework"
 
 # If not set, the OpenCI would download the tarball from Github every time.
-mbedtls_archive="${mbedtls_archive:-$tfa_downloads/mbedtls/mbedtls-2.25.0.tar.gz}"
+mbedtls_archive="${mbedtls_archive:-$tfa_downloads/mbedtls/mbedtls-2.26.0.tar.gz}"
 
 # Arm Coverity server.
 export coverity_host="${coverity_host:-coverity.cambridge.arm.com}"
diff --git a/script/tf-coverity/common-def.sh b/script/tf-coverity/common-def.sh
index a7ec236..f2241ec 100644
--- a/script/tf-coverity/common-def.sh
+++ b/script/tf-coverity/common-def.sh
@@ -71,7 +71,7 @@
 
 # mbed TLS source tag to checkout when building Trusted Firmware with Trusted
 # Board Boot support.
-MBED_TLS_SOURCES_TAG="mbedtls-2.25.0"
+MBED_TLS_SOURCES_TAG="mbedtls-2.26.0"
 
 ARMCLANG_PATH="$(set_armclang_toolchain)"
 
diff --git a/utils.sh b/utils.sh
index 5d3d6e0..b285087 100644
--- a/utils.sh
+++ b/utils.sh
@@ -336,12 +336,10 @@
 
 linaro_2001_release="${linaro_2001_release:-$tfa_downloads/linaro/20.01}"
 linaro_release="${linaro_release:-$linaro_2001_release}"
+mbedtls_version="${mbedtls_version:-2.26.0}"
 
 # mbedTLS archive public hosting available at github.com
-mbedtls_archive="${mbedtls_archive:-https://github.com/ARMmbed/mbedtls/archive/mbedtls-2.25.0.tar.gz}"
-# The tar file contains mbedtls-mbedtls-2.25.0 repo which holds the necessary
-# source files of mbedTLS project
-mbedtls_repo_name="${mbedtls_repo_name:-mbedtls-mbedtls-2.25.0}"
+mbedtls_archive="${mbedtls_archive:-https://github.com/ARMmbed/mbedtls/archive/mbedtls-${mbedtls_version}.tar.gz}"
 
 coverity_path="${coverity_path:-${nfs_volume}/tools/coverity/static-analysis/2020.06}"
 coverity_default_checkers=(